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A rudimentary neurohaemal organ, the storage zone, has been observed in the cerebral ganglion and there appears to be another neurohaemal area in the ventral nerve cord ganglion. The storage zone is formed by the terminal ends of the axons of A cells. The chrome alum haematoxylin phloxin (CHP) and aldehyde fuchsin (AF) positive substances in the form of granules are found in this area. The cerebral ganglion is richly supplied by blood capillaries. The distal end of the axons of B cells are swollen like a bulb while in some cases the axons are united to form an axonal tract. Extra-cellular material is abundant in different parts of the nervous system. In all cell types, the perinuclear zone is the first to show activity in the secretory cycle. It appears that the nucleus may be involved in the elaboration of the neurosecretory material in the cells.Neurosecretory cells with endocrine functions have been demonstrated in most major groups of triploblastic animals. Endocrinological studies were initiated in annelids by Scharrer ('36), though the neurosecretory cells were shown but misinterpreted by Hamaker (1898). Since then, the endocrinology of annelid worms has been the subject of a large number of experimental and ultrastructural investigations. Divergent opinions continued to be expressed about the types of the neurosecretory cells actually present in Oligochaeta. Scharrer and Scharrer ('37, '45, '54) Current evidence indicates that neurosecretory material is produced in the perikaryon of the cells, passes into the axons where it is temporarily stored and then released through the axon bulb (Rothballer, '66; Scharrer, '66; Dogra, '68). The mechanism of the release of the neurosecretory material has been considerably debated in recent years (De Robertis, '62; Heller and Lederis, '62; Knowles, '62; Bern, '63). The axon bulbs have special significance for the neurosecretory neurones, which combine the function of ordinary neurones with that of glandular cells. Furthermore, unlike the ordinary neurones, the neurosecretory cells do not form synapses by terminating a t the effector organ but instead they release their hormones either directly into the blood (Clark, '59, '661, or into an intermediate structure-the storage and release organ (Scharrer, '63). It is possible that there are two secretory pathways, an intra-cellular and inter-cellular, for the transportation of the neurosecretory material elaborated by the perikaryon (Dogra, '68). With the discovery of the neurohaemal organs, a neurosecretory x-organ sinus gland system in crustacea and inter-cerebralis-cardiacum-allatum system in insects have been established but such a system is still not known for annelids.It appears that the variations in the morphology of the neurosecretory cells, different ways of synthesis of hormones in these cells and the various modes of release of hormones in the absence of a well developed storage and release organs are of common occurrence in oligochaetes. The present paper describes the structure of the various types...

This comprehensive study was undertaken to reveal the ovarian histomorphology in the oligochaetous clitellte, Dendrobaena atheca Cernosvitov. Efforts were, in fact, made to obtain proper histological preparations. So, various types of thin serial sections of ovaries were carefully obtained, stained and examined. Two small ovaries, at the beginning of breeding seasons, were seen in segment thirteen. Subsequently, they extremely increased in size and became fully formed. They demonstrated six principal cell types: peritoneal cell, follicular cell, stromal cell, oogonium, oocyte and trophocyte (nurse cell). The first three cell types were somatic, whereas the other three were germ and germ-line. All cell types were, as much as possible, properly described. Dividing oogonia were seen to produce oocytes and trophocytes simultaneously. The produced cells were seen to be interconnected. The stromal cell, a newly described cell type, exhibited several specific cell characteristics. Ovaries showed no internal lumens. The small ovaries showed only two distinct histological zones, whereas the large ones showed three such zones. Germ and germ-line cells showed an obvious arrangement in ovarian zones. Accordingly, the chief conclusions are: (1) ovaries are nutrimental due to presence of trophocytes (2) ovaries are solid and not sac-like organs due the lack of internal cavity (3) stromal cell can be considered a new cell type as it demonstrates several specific cell features (4) Ovarian zonation is caused by production and arrangement of germ and germ-line cells (5) intercellular connections are due to incomplete cell divisions.

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