400 M. Victor Faussek on the Anatomy and 



nucleus in Zicglcr's * sense ; the nuclei, however, do not lose 

 their histogenctic property (see below). The study of the 

 fragmentation of the nuclei has led me to wonder whether it 

 may not be that the so-called " secondary mesoderm " of the 

 Crustacea {AstacuSj according to lleichenbach) represents no 

 cellular elements, but nuclei in the state of fragmentation. 



6. The mesoderm is formed, as has been stated, from the 

 ectoderm ; but during the first ])eriod of development a few 

 elements of endodcrmic origin are also added to it ; these are 

 large cells which split off from the endoderm cells (figs. 13 

 and 16). A small number of them separate from the endo- 

 derm cells lying peripherally immediately beneath the primi- 

 tive streak, and are soon indistinguishable from the cells of 

 the latter ; for this reason I was unable to ascertain their 

 subsequent fate. 



7. It has already been mentioned that the rudiment of the 

 germ-cells appears in the ectoderm at a very early period and 

 projects into the interior of the ovum. In the earliest stages 

 differences in the germinal rudiment may already be perceived 

 in certain ova. In some cases the rudiment consists of cells 

 with large nuclei, but in others their nuclei do not differ much 

 from those of the cells of the primitive streak. The first 

 stage in the further development of the rudiment of the sexual 

 organs consists in its separation from the ectoderm ; its cells 

 become superficially covered by a layer of ordinary ectoderm 

 cells (fig. 17). In somewhat later stages the rudiment of the 

 sexual organs lies sunk in the abdominal nervous svstem 

 (figs. 18 and 19) ; after the nervous system withdraws into 

 the ccphalothorax, however, the germinal rudiment remains 

 in the abdomen behind the ccphalothoracic ganglia, where it 

 now appears between two layers of mesoderm, V. e. enclosed 

 in the ccclom (figs. 19, 20, and 21). In subsequent stages 

 the germinal rudiment with the large nuclei considerably 

 increases in size, and after the emergence of the embryo serves 

 to form the female generative organs (figs. 20, 22, 23, 27, 28, 

 and 29). The germinal rudiment of the second kind (that 

 "which consists of cells with small nuclei) remains of incon- 

 siderable size and becomes transformed into the male gcnc- 



* Ziegler, " Die Entstehung des Blutes bei Knocheufiscliembryonen," 

 Arcliiv f. mikrofk. Aiiatoniit', JlO IW. AVhile my memoir was in the 



1)ress there nppeaivd the iiilerestinjr pa]iers of Ziejrler on " l^ie biologisohe 

 Jedeutung dor amitotisclieii (direkteii) Keriitoilinijr im Tierreich," IJiolo- 

 gisches C'entralbhitt, xi. Bd. uos. 12 and 13 l-^'^"- '■'^' ^"c- ^'^'- ^ii-^t. 

 ser. (i, voL \iii. Nov. 1801, "The ]{iohigiral Import of Amitotic (Direct) 

 Kiielear Division in the Animal Kingdom," pn. o&2 oSO"), and Frenzel, 

 " Zur Deurteihmg der aniitoti^idion (direkteu) Keruteiluug,'' ibiii. uo. 18, 

 of which I was unable to avail mvself. 



