758 I5EP0RT — 1887. 



have separated, either apparently or in reality, into four and sometimes even eight 

 fragments. Could the presence of the male nucleus have by any chance escaped the 

 notice of Zacharias ? ... In all the nematoids I have studied, I have nearly 

 always ascertained the progressive elaboration of the female nucleus, whilst at the 

 same time the male nucleus, vphich was visible at the various stages, was gradually 

 developing. Then, again, in such species as the Ascaris clavata, where the equa- 

 torial division takes place, the ultimate nucleus of the e^^ is completed, as at the 

 end of the ordinary kinesis. 



In short, if the first mode exists, viz. the normal mode of Zacharias, it seems to 

 me but to represent a special and, perhaps, an eventual mode of fecundation in the 

 nematoids. Whether the fusion of the male and female nucleus takes place at the 

 top of the e^oTj or later after their distinct elaboypticn. or lastly during the kinesis 

 of segmentation, it matters little ; at all events the fusion, in my opinion, does take 

 place, and that is tlie essential point. I muht, therefore, on this subject, maintain 

 my former conclusions. 



I shall be happy to put at the disposal of my learned colleagues, to whom the 

 matter may be of interest, a number of preparations obtained from varioua 

 nematoids. 



4. The Spermatogenesis of the Acarians and the Laius of Spermatogenesis 

 in general. By Professor GiLSON. 



This paper is but a very short abstract of a chapter of my work upon the sjier- 

 matogenesis of the Arthropods, which is still in course of publication. The original 

 paper would have been too long to read in French without exhausting your patience, 

 but on the other hand I must claim your indulgence for this Englisli abstract. 



The spermatozoa of this group of Arthropods are not yet very much known. 



Leydig and Pagenstecher give only a few drawings and a very short description 

 of them. Claparede and Henking have also studied the spermatozoa of Atax, 

 Tetranychus, and Trombidium. But these are — according to their drawings — 

 thoroughly different from those we have found in the Gamasids and the Ixodids. 

 These bodies show, however, very interesting features in their constitution and 

 genesis. 



The multiplication of the mother-cells, which give origin to the spermatic cells, 

 takes place by bmary segmentation. The spermatic cell contains a large nucleus, 

 in which a little nucleolus is visible. In this are enclosed the bits of nucleinic 

 substance (or chromatin) perfectly colourable by the methyl-green. 



According to the appellation proposed by Professor Carnoy for that kind of pro- 

 ductions this nucleolus is to be called in French ' nucl^ole-noyau,' and could be 

 called in English ' nucleo-nucleolus,' or nucleus-shaped nucleolus. 



This cell grows longer into a rather thick spindle. The nucleus takes also a 

 lengthened shape. But the nucleus-shaped nucleolus remains intact in form and 

 in internal structure. 



Under the membrane of the cells appear longitudinal or transversal lines, 

 according to the species. Tho.se details depend on the external layer of the proto- 

 plasmic reticle which is contiguous to the membrane. In the same time the 

 lengthened true nucleus becomes iucrusted with a hynlin substance. 



In several species the nucleu.s-shaped nucleolus pierces the cell's membrane, and 

 remains entangled in the same and externally prominent. 



The spermatozoa are free; ordinarily unmoved in the male; animated with 

 light contractions in the female. 



Many might consider that the spermatogenesis of those animals I have just 

 shortly described is a deviation from what they would call the (/ene7-al law of sper- 

 matogenesis. As for me I rather think that there is no general law existing for 

 the spermatogenesis. 



The phenomena of the genesis and the differentiation of the spermatic cell are, 

 indeed, extraordinarily diver.sified — to such a point that, in order to get them 

 together in a single formula, it would be necessary to say : the development of sper- 

 matozoa includes several different processes of cellular genesis and differentiation. 



