OF THE GERM CELLS OF METAZOA. 181 



140); and in the dyaster stage of the second maturation division (Fig. 141) we see in 

 each daughter cell (spermatid) the chromosomes densely apposed, forming together a 

 rounded, irregular mass, and in only one of the two daughter cells the chromosome x i. 

 The reduction of the number of chromatin elements in Protenor belfragei is accord- 

 ingly as follows : Spermatogonium, two univalent chromatin nucleoli, ten univalent 

 chromosomes, one chromosome x ; first spermatocyte, one bivalent chromatin nucleolus, 

 five bivalent chromosomes, one chromosome x; second spermatocyte, one univalent 

 chromatin uucleolus, five univalent chromosomes, one-half chromosome x; spermatid, 

 one semivalent chromatin nucleolus, five semivalent chromosomes, and either present or 

 absent one-half chromosome x. This chromosome x is the odd one of the spermato- 

 gonia ; it does not unite with any other one in the synapsis stage of the spermatocyte, 

 yet since it sometimes appears bipartite in the synapsis and undergoes a transverse divi- 

 sion in the first maturation mitosis, it may perhaps be looked upon as bivalent in both 

 spermatogonium and spermatocyte. If this is a correct conclusion, then the uneven 

 number of chromosomes in the spermatogonia would be the result of two univalent ones 

 remaining there united instead of separating this compound, bivalent one being the 

 chromosome x. This chromosome, as we have seen, behaves in the rest stage of the 

 spermatogonia like the other chromosomes, but in the growth period of the spermatocytes 

 it acts in many ways like a chromatin nucleolus. 



23. Cymus augiistatus Stal. 



Rix testes of this species were studied. 



There was no material at my service fixed with Flemming's or Hermann's fluids, so 

 not being able to use the triple stain of Hermann I was unable to determine the relations 

 of the chromatin nucleoli in the rest stage of the spermatogonia. The preparations also 

 showed no favorable cells for counting the chromosomes in this generation. 



In the synapsis stage there is a rather small, dumbbell-shaped, and so probably 

 bivalent, chromatin nucleolus, which becomes spherical in the following (complete) rest 

 stage of the spermatocyte. 



There were no pole views of the chromosomal plate of the first maturation division, 

 but two pole views of the succeeding dyaster are here given (PL IV, Fig. 143, showing 

 the chromosomes before taking their definite position in the spindle, while in Fig. 144 

 they occupy this position and are seen from their ends) ; here can be counted twelve 

 chromosomes and one smaller body (N. 2, probably the chromatin nucleolus, very small 

 in Fig. 144). On lateral views of the first maturation monaster (Fig. 142, which, how- 

 ever, shows only nine of the elements), all the chromosomes usually appear dumbbell- 



