The hypothesis was confirmed that postoperative disturbances of preoperatively learned light-discrimination habits are due to sensory impairments and not losses of memory. The experiments also suggested that the striate rat discriminates on the basis of luminous flux and indicate that Kliiver's analysis of the residual visual capacities of the striate monkey should be extended to the rat.

The insect pathogenic fungus Metarhizium anisopliae produces several extracellular cuticle-degrading proteases and evidence is consistent with one of these, PR1, which is a chymoelastase, being a determinant of pathogenicity. We have shown previously that P R l production is regulated by both carbon catabolite and nitrogen metabolite repression and also by specific induction under derepressed conditions by insect cuticle. In the present work we have established that an enzymically released proteinaceous component(s) of insect cuticle is capable of inducing PR1 (based on appearance of extracellular activity). Cuticle of the desert locust Schistocerca gregaria treated with KOH to remove protein failed to induce PR1 production, whereas cuticle treated with either chloroform or ether to remove lipids still induced PR1. Cuticle digested with either PR1 or the trypsin-like PR2 of M. anisopliae released peptides mainly in the range 150-2000 Da; addition of these peptides generated by PR1 or PR2 a t 3 pg alanine equivalents ml-1 induced PR1 production to a level similar (75 O/ O) to that obtained with untreated insect cuticle. Several amino acids and peptides which are abundant in insect cuticular protein (Ala, Gly, Ala-Ala, Ala-Ala-Ala, Ala-Pro and Pro-Ala) were tested at a range of concentrations and in restricted cultures for their ability to induce PR1. None induced the protease to the levels seen with cuticle or peptides enzymically released from cuticle, although some dimers and notably the monomers Ala and Gly gave 2-2.7-fold enhanced PR1 activity above derepressed basal levels (up to -57% of that achieved with induced synthesis on cuticle). There was evidence for more efficient uptake and/or catabolism by M. anisopliae of alanine di-and tripeptides than of monomer amino acids.

Rats were subjected to visual-cortex damage either at 1 day of age or in adulthood and their ability to utilize pattern cues was assessed. No age effect was obtained. This was true for Ss with all or part of visual cortex removed and for Ss maintained postoperatively in visually rich, poor, or ordinary lab environments. The study did demonstrate, however, that Ss with visualcortex damage tend to use luminous flux cues while normal SB tend to use pattern cues in performing a brightness discrimination task, and further, that performance of the brightness discrimination task by Ss subjected to tissue removal can be affected by lesion size. EXPERIMENT 1The primary purpose of this study was to determine whether early visual-cortex damage is visually less incapacitating than later damage. Some suggestive evidence for this possibility can be found from work on the rat (Tsang, 1937) and on the cat (Doty, 1961; Wetzel, Thompson, Horel, & Meyer, 1965). In Experiment 1 the pattern vision of rats operated at 1 day or 3 mo. of age was assessed after equal postoperative recovery periods. These Ss as well as control Ss were first trained to perform an 8:1 light discrimination and then given transfer tests designed to determine whether the animals were using pattern or luminous flux cues in learning the discrimination. In addition, Ss were trained on a horizontal vs. vertical stripes pattern discrimination. MethodSubjects. The 14 male and 13 female Long-Evans black-hooded rats were divided into four groups; a neonatal visual-cortex ablation group (NL, n -6); a neonatal operated-control group (NC, n = 7); a 3-mo.-old visual-cortex ablation group (AL, n -7); and a 3-mo.-old normal-con-

Unilateral subtotal collicular and, large but not small, unilateral posterior cortical lesions in rats produced ipsiversive progression tendencies in a visual task. However, no support could be given to the view that the progression tendencies following unilateral collicular lesions are in part a reflection of contralateral visuosensory-field deficits. Thus, performance of a light-dark task was equally good when vision was restricted to the eye leading to the damaged colliculus as when restricted to the eye leading to the undamaged collicullus. la addition, bilateral collicular lesions had no effect on performance of either the light-dark or a stripes discrimination task. The study indicated the need for caution in basing interpretations of the nature of vision on simple response tendencies.

Visual decortication failed to affect rate of acquisition of 1-min. delayed CERs when either light alone or noise alone provided the CS. However, CER paradigms involving a combination of light and noise CSs revealed differences in behavior between experimental and control animals. Decorticate rats transferred the CER from light to noise (although not from noise to light). Normal animals showed no transfer. Decorticate animals were conditioned to a noise CS in a paradigm which prevents conditioning in normal subjects. Also, decorticate rats were better able to discriminate a compound light-noise CS from light-alone and noise-alone CSs. Partly from these findings, partly because the abnormal behavior of the decorticate subjects is mimicked by normal animals wearing light-diffusing eye occluders, and partly from other considerations, it was speculated that vision as a qualitatively unique sensory modality is undermined by visual cortex destruction.The nature of vision in animals lacking visual cortex appears to be in dispute. Kliiver's (1942) study, considered by some to be the classic one in the field, suggests that the visually decorticate animal is reduced largely to the use of luminous flux cues. However, work prior to Kliiver's study (e.g.,