BEPRODUCTIVE ELEMENTS IN APUS AND BRANCHIPUS. 275 



many points are worthy of attention. Scattered through the egg 

 mother-cells are numerous groups and rows of nuclei^ obviously 

 of a different character from those destined to form the eggs 

 (figs. 20, 21, 43, &c.). These nuclei are very irregular in out- 

 line, and of a fine reticulate appearance. They show numerous 

 figures of direct division (figs. 20, 43). At the same time it is 

 quite easy to establish a gradational series extending from the 

 true egg, forming nuclei on the one hand to the irregular 

 akinetically dividing elements on the other, the latter class 

 being always intimately and actually concerned in the secretion 

 of a peculiar slimy substance (fig. 44) ; and this slime in turn 

 is ultimately worked up in the lower portion of the tube to 

 form the ornamental egg-case, so that although in the egg 

 formation in Branchipus the primitively similar genital cells 

 (male ova) diverge along two ways, one leading through succes- 

 sive karyokinesis to the final eggs, they ultimately both co- 

 operate in the perpetuation of the species by the rest being 

 bodily transmuted into the ornamental case in which the eggs 

 are laid. This duality in the ovarian elements is interesting in 

 the sense that it offers a precise parallelism to the dualism caused 

 in the spermatic apparatus by the presence of the akinetically 

 dividing foot-cells, over whose significance so much controversy 

 has at times been raised. In Branchipus the foot-cells are 

 more regularly arranged than the above akinetically dividing 

 elements in the ovary. At the upper end of the gland they 

 occur at intervals of about ten cells in all directions, and, true 

 to their female homologues, are more numerous as we descend 

 towards the genital aperture. Apart from the function of the 

 foot-cells no one can be in doubt as to their homology with the 

 above akinetically dividing elements of the ovary ; and the fact 

 that the latter are intimately bound up with the formation of 

 the slime that makes the egg-case (slime-cells) seems to me to 

 remove all doubt from vom Eath's theory, that in the sperma- 

 togenesis they are concerned in the secretion of a fluid in which 

 the spermatozoa are suspended. The key to the whole position 

 seems to lie in the observation of La Valette St. George, that 

 the mulberry-shaped masses of the spermatocytes in Blatta are 



