OCR Text |
Show 1901.] FROM BRITISH EAST AFRICA. 351 this worm a peculiar compact body, " whose structure I was unfortunately unable, on account of the unfavourable preservation of the material, to understand. The whole interior of this body appeared to be formed of a structureless granular mass. An outer .... layer encloses this mass. This outer layer seemed to me to possess a cellular structure" '. Michaelsen then suggested the possibility that this body was an embryo-a by no means unnatural suggestion in view of its size and appearance in a badly preserved specimen. I emphasize, however, the remark that the outer layer appeared to be of a cellular nature ; as this opinion was no doubt founded upon the observation of the deeply staining bodies, which, I think, must be the nuclei of the cells lining the spermatheca. I a m far from asserting, however, that the outer case of the spermatophore is a layer of living cells. This may be so; but in the meantime I should regard it rather as produced by the broken down debris of the cells of the spermatheca, including liberated nuclei, all of which will possibly lose their characters as the spermatophore gets riper. The facts, however, so far do not permit, as I think, of a decisive statement of opinion. So far, then, the case of the spermatophore appears to be a product of the spermathecal sac where it is found. At the head-end of the spermatophore the case is filled with the dark granules already mentioned, which are particularly thickly clustered along the narrow beak. The cells of the spermathecal sac contain no granules of this character. They are like those of the chloragogen cells ; but in this particular worm I noticed no chloragogen cells which might serve to explain the origin of the granules. The only place where there were cells filled with such granules were the innermost layer of cells of the spermiducal gland. The evidence seems to m e therefore to be strongly in favour of the view that the wall of the spermatophore in the head-region is derived from materials existing in the spermiducal glands. The final plug of granular matter must therefore be added after the spermatozoa have been injected into the spermathecal sac from the male orifice. There is a remarkable analogy here with tbe (or a) supposed use of the prostatic fluids in mammals. It has been held that it serves as a plug to retain the sperm in the female organs, and it may apparently harden into a definite plug useful for that purpose. The use of spermatophores of the type described here may be largely to prevent the sperm from wandering and from finding its way out of the receptacle intended for its storage. But it must be remembered that we are at present in absolute ignorance of the wav in which fertilization is effected in these Annelids. (4) On the Ovaries, Oviducts, and Sperm-ducts of Stuhlmannia. Although the maiu features in the structure of this Eudrilid genus have been amply elucidated by the careful observations of 1 The italics are mine, |