Studies on Chromosomes 79 



bar" in the dividing oogonia, and in the connective tissue cells of 

 the ovary, and also figured (Fig. 39) a double group (exactly such 

 as I described in Anasa, Wilson '06, Fig. 2,k), showing forty-eight 

 chromosomes. 



Gross accepts Henking's account without question, treating the 

 numerical relations in rather summary fashion as follows: "Die 

 Aequatorialplatte der sich teilenden Spermatogonien enthalt 24 

 Chromosomen. Dieselbe Zahl hat Henking ausser in den Sperma- 

 togonien auch in den Oogonien gefunden. Ebenso konnte ich in 

 den Follikelzellen der Eirohren, also in somatischen Zellen, kon- 

 statieren. 24 ist also die Normalzahl der Species" ('07, p. 277). 

 In support of this are given two polar views of spermatogonia! 

 metaphases (the female groups are not figured) each showing eight 

 small and sixteen large chromosomes (Figs. 9 and 10). His ac- 

 count continues as follows: The idiochromosome appears aready in 

 the syanaptic period (synizesis) as a double nucleolus-like body, 

 assumed to be a bivalent body that arises by the synapsis of two 

 of the spermatogonia! chromosomes, though none of the earlier 

 stages were followed out. At a later period it appears as a single 

 spheroidal body owing to the close apposition of its two halves. 

 This chromosome divides in the first spermatocyte division, but 

 in the second lags behind the others and passes undivided to one 

 pole, as Henking described. All of the spermatid-nuclei thus 

 receive eleven chromosomes, while half of them receive in addi- 

 tion the idiochromosome. Since both sexes were supposed to con- 

 tain twenty-four chromosomes, Gross drew the same conclusion 

 as the one previously reached in the case of Syromastes, namely, 

 that only the twelve-chromosome spermatozoa are functional. 



In regard to the spermatocyte divisions my own results are 

 perfectly in accord with Henking's and Gross's. As to the 

 spermatogonia! number, I must say that after having immediately 

 confirmed Gross's account of Syromastes (which I examined first) 

 I was fully prepared to find a similar relation in Pyrrochoris. It 

 was therefore with astonishment that I found everywhere twenty- 

 three instead of twenty-four spermatogonia! chromosomes. This 

 number appears with diagrammatic clearness in a great number of 

 spermatogonia from different individuals (testes from 35 different 



