îhe Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 33 



in which no cell boundaries can be distinguished (though each mass 

 is enveloped by a membrane), and are especially characterized by 

 their large amount of cytoplasm and yolk. The syncytia may or may 

 not be more or less separated by a clear space from the more numerous 

 cell-walled cells which lie between and around them, and which have 

 formed the basis of the preceding description. Each such mass is a 

 cell syncytium, in which the nuclei are rarely grouped at regular 

 distances from one another, but are usually collected together in a 

 group, the rest of the syncytium then consisting entirely of cytoplasm. 

 The nuclei have the same structure as those of the other cells at a 

 corresponding stage. The cytoplasm is denser towards the centre of 

 the syncytium, where yolk is abundant and in all stages of formation ; 

 while at the periphery of the syncytium the cytoplasm is free of yolk 

 substance, and is here vacuolar, the vacuoles frequently elongated and 

 then parallel to the surface of the syncytium. In the neighborhood of 

 the yolk substance, on preparations fixed with Hermann's fluid, the 

 cytoplasm has a peculiar deep brown tinge, probably due to trans- 

 fused yolk substance; and the difficulty in detecting the idiozomes of 

 these cells is probably due to the presence of this substance. No 

 cell membranes occur within the cytoplasm. Each syncytium may, or 

 may not, constitute a whole spermatocyst ; in the latter case the 

 syncytium may occupy the centre of the spermatocyst, as shown in 

 Fig. 93, or it may lie excentrically , surrounded by the usual type 

 of cells. 



The nature and economy of these syncytia is probably to be 

 explained by assuming them to be groups of cells which have received 

 a richer nutritive supply than the other cells of the testicle. This 

 assumption agrees with the facts of the large amount of cytoplasm 

 and yolk, the latter substance certainly being a product of nutritive 

 metabolism. The component cells of the syncytia become separated 

 from one another shortly before the rest stage of the spermatocytes; 

 but in that zone of each follicle of the testicle where the resting 

 stages occur are found small syncytia of cells of 2 or 3 each, which 

 appear like bi- or trinucleated cells on account of the absence of 

 limiting membranes, and such small syncytia are fragments of the 

 larger ones found in the telophase and synapsis. The cells of the 

 small syncytia develop normally, making the reduction divisions in the 

 same way as do the isolated cells, and producing normal spermatids. 

 But since in them two or three nuclei occur side by side, the two or three 

 spindles are usually parallel to one another, and not perpendicular as 



Zool. Jahrb. xn. Abth. f. Morph. 3 



