An improved technique is described for in vitro culture of the chick embryo from three days through 21 days of total incubation (three days in shell plus 18 days in culture). Mean survival time for cultured embryos is 18 days of total incubation, and mean morphological stage is Hamburger-Hamilton stage 41 (15 days). Mean measurements of wet weight, dry weight, and right third toe length for stage 45 (partial or complete abdominal yolk sac retraction, 19-20 days) cultured embryos are comparable with corresponding means for stage 42-43 (16-17 days) embryos from control intact eggs. Possible causes of growth retardation in vitro are briefly discussed.

Spermiogenesis in Macrostomum lignano (Macrostomorpha, Rhabditophora) is described using light- and electron microscopy of the successive stages in sperm development. Ovoid spermatids develop to highly complex, elongated sperm possessing an undulating distal (anterior) process (or "feeler"), bristles, and a proximal (posterior) brush. In particular, we present a detailed account of the morphology and ontogeny of the bristles, describing for the first time the formation of a highly specialized bristle complex consisting of several parts. This complex is ultimately reduced when sperm are mature. The implications of the development of this bristle complex on both sperm maturation and the evolution and function of the bristles are discussed. The assumed homology between bristles and flagellae questioned.

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In two trials, SC White Leghorns were subjected to constant ambient temperatures of 21.1, 29.4, and 35.0 C from 2 to 31 or 32 weeks of age. Weekly measurements were made of body weight, feed efficiency, water consumption, red blood cell count, hemoglobin, hematocrit, total plasma protein, Po2, Pco2, pH, and mortality. It was found that the blood picture changes with age, sex, and ambient temperature. Age at which sex differences become significant varies with the blood component studied.

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