of Edinburgh, Session 1885 - 86 . 
809 
Herrmann has described the spermatogenesis of certain Crustacea 
as consisting in the division of the nucleus of a male ovule to form 
a group of spermatoblasts, each of which becomes differentiated into 
a spermatozoon. A more thorough investigation, however, is due to 
Grobben. The germinal layer of the Crustacean testes is described 
as consisting of (a) large cells with round nuclei (the spermatoblasts 
of Von Ebner, &c.), and (6) of a nucleated protoplasmic mass between 
the bases of the former. The reserve nucleated masses ( Ersatzkeime ) 
represent, according to Grobben, the earliest stage ; the larger nuclei 
are changed into spermatoblast-nuclei, while the former probably 
multiply and grow for the future replacement of used-up spermato- 
blasts. Each of these reserve germs (Ersatzkeime) is potentially a 
spermatoblast; the difference between them is secondary. The 
comparative spermatogenesis of Arthropoda has lately been the 
subject of elaborate study by Gilson, who distinguishes primor- 
dial “ metrocytes,” multiplying into direct metrocytes or “ mother- 
sperm cells,” which divide up into “ spermatic cells ” — each the 
immediate predecessor of a spermatozoon. 
Sabatier (1882) has also described the spermatogenesis of several 
Invertebrates. Within mother-cells or “ spermatospores ” nuclear 
multiplication and superficial budding occur, resulting in a number 
of stalked claviform cells or “ protospermoblasts.” These are 
detached, increase in size, exhibit nuclear multiplication and super- 
ficial budding, resulting in the production of a second generation 
of spermoblasts — the “deuto-spermoblasts,” which form the spermato- 
zoids. In regard to numerous groups, Nemerteans, Echinoderms, 
Molluscs, and Ascidians, he maintains the occurrence of two 
generations of cells of which the first become the blastopliores of 
the second, the “spermatospores” of the “protospermoblasts,” and 
the latter in turn of the “ deuto-spermoblasts.” 
Most nearly related perhaps to Sabatier’s account is the divergent 
description given by Bolles-Lee of the spermatogenesis of Appendicu- 
laria. In the large mother-cells of the testis scattered nuclei appear, 
originating, however, not from the mother-cell nucleus, but, peripher- 
ally, from the protoplasm. There is, further, no “ polyplast ” stage, 
but the developed nuclei, i.e., the “spermatoblasts,” form a 
“ germinative epithelium,” and are differentiated on the surface into 
spermatozoa. 
