448 SUMMABY OF CURKENT RESEARCHES RELATING TO 



two or three, the mother-cells ; they are round, with granular proto- 

 plasm and nucleus ; there is a small but strongly refringent nucleolus, 

 and a very delicate cell-wall. 



The spermatozoa are formed within the mother-cell by dichotomous 

 division of the nucleus, resulting in the production of eight to 

 twelve nuclei ; when these are formed the protoplasm itself divides 

 and becomes aggregated around the different nuclei, which continue 

 to divide until from twenty to thirty daughter-cells are formed ; 

 their nuclei have all the characters of the original nucleus of 

 the mother-cell ; each occupies nearly the whole of its cell ; the 

 mother-cell now has a distinct doubly-contoured wall , consisting of 

 the old cell-wall strengthened by the adhesion to it of the peripheral 

 layer of protoplasm, and is consequently a cuticular or non-cellular 

 structure in this case, whatever it may be in Insects. The nuclei 

 now undergo great changes ; their granules decrease in number, 

 increase in size, and then unite to form a single mass, which then 

 elongates and assumes a horseshoe shape ; the horseshoe breaks up 

 into four, six, and finally eight parts which adhere to the nuclear 

 membrane ; the latter and its liquid contents are now absorbed and 

 each portion of the altered nucleus becomes directly surrounded by 

 the protoplasm of the daughter-cell, and constitutes thereby a cell of 

 the tertiary order. These latter cells escape into the mother-cell at 

 the sexual period, by rupture of the walls of the daughter-cells, form- 

 ing the spermatozoa which finally reach the vas deferens by rupture 

 of the capsule of the mother-cell. The mature spermatozoa are 

 biconvex lenticular bodies, "003 mm. in diameter, rendered most 

 convex in the centre by their nucleus ; they exhibit no true indepen- 

 dent movements, but are impelled by simple vis a tergo as far as the 

 muscular bulb of the vas deferens, which then contracts and sends 

 them to the end of the penis into the terminal gland, and into the 

 receptacula seminis. The nuclei of some of the mother- or daughter- 

 cells are liable to suffer a degeneration, by which the granules, and 

 even in some cases the cell-protoplasm itself, become replaced by a 

 number of small bodies, and in this condition refract brilliantly ; 

 such cells are also observed in some Crustacea ; they appear to be 

 neither calcareous nor fatty in composition. 



In the female organs Dr. Blanc finds a pair of receptacula seminis, 

 which vary in form, opening into the vagina ; their function is decided 

 by the spermatozoa which they have been found at certain times to 

 contain. The ovum, which has a delicate vitelline membrane, 

 increases immensely in size while in the oviduct, distending this 

 tube ; a pressure is thus applied to the adjacent receptacula seminis 

 and sjDerm is extruded ; the writer assumes the occurrence of amoeboid 

 movements of the spermatozoa, to account for the penetration by 

 them of the vitelline membrane. With regard to the question of 

 hermaphroditism, it is placed beyond doubt that ova often do occur, 

 chiifly in young individuals, on the surface of the testes, manifesting 

 the same pedunculate mode of attachment and the same structural 

 characters as in the ovary itself. It is only male individuals which 

 exhibit the phenomena of hermaphroditism ; and these phenomena 



