OK THE GERM CELLS OF METAZOA. 



191 



five are seen on lateral view and five on pole view, all these elements not having taken 

 their definite position in the equator of the spindle). All are bivalent, as is proved by 

 their bipartite appearance on lateral view. One of them is smaller than the others, and 

 may represent the large (bivalent) chromatin nucleolus of the growth, period (K '2, Fig. 

 206), while the nine remaining elements are probably chromosomes ; if Ibis interpretation 

 be correct then the small (univalent ?) chromatin nucleolus found in the growth period 

 would not be represented in the first maturation division. 



iMcmivnn.K 



34. Acholla multispinom De G. 



Eight testes of this species were studied. 



The relations of the minute chromatii cleoli could not be determined in the rest 



stage of the spermatogonia. 



In the mosl favorable pole view of a. spermatogonic monaster (PI. V, Fig. 207) could 

 be counted thirty-one chromatin elements. The twenty-four larger elements seen here are 

 univalent chromosomes, the seven smallest are chromatin nucleoli (some of them very 

 minute). Of the latter there are six arranged in three pairs and one that is isolated. 

 Now we shall find that in the spermatocytes there are lour bivalent chromatin nucleoli 

 (Figs. 208-211), so that in the spermatogonia there should be eight ; and accordingly 

 though oidy seven are to be seen in Fig. 207, we arc justified in concluding that an eighth 

 must be present there but hidden from view by one of the chromosomes. Thus there 

 would be in the spermatogonium in all probability twenty-four chromosomes and eight 

 chromatin nucleoli, in all thirty-two elements. 



In the synapsis stage of the growth period the twenty-four chromosomes unite lo 

 form twelve bivalent ones. The eight chromatin nucleoli likewise combine to form four 

 bivalent ones, which near the close of the growth period (Figs. 208, 209) are seen to be 

 small bodies attached to the surface of the true nucleolus {N). Each is dumbbell-shaped, 

 usually with its component univalent parts in close apposition, but occasionally the latter 

 are more or less separated from one another. 



Pole views of the monaster stage of the first maturation division (Fig. 210) show six- 

 leen elements, namely, twelve larger, bivalent chromosomes (dumbbell-shaped on lateral 

 view) and four much smaller chromatin nucleoli (N. 2). All these elements are halved 

 in the following metakinesis, which is a transverse (reduction) division, and pole views of 

 the daughter cells (second spermatocytes, Fig. 211) show twelve larger, univalent chromo- 

 somes and four smaller, univalent, chromatin nucleoli (A r . :.'). 

 A. p. s. — vol. \\. v. 



