Studies on Chromosomes 87 



The correctness of my deduction may readily be tested by a 

 reexamination of the female groups. Gross, it is true, states 

 that he has found but twenty-two chromosomes in the female 

 (follicle cells); but I think no one is likely to consider as in any 

 way conclusive the single figure that he gives in support of this 

 (op. cit,, Fig. III). Not less than five of the twenty-two chromo- 

 somes figured are deeply constricted; and any one of these might 

 in reality be two chromosomes in contacti I hope that Dr. 

 Gross himself may be willing to reexamine this point, in view of 

 the possibility here suggested. It is however also possible that the 

 two members of each of the idiochromosome pairs in the female 

 may be united to form a bivalent, in which case the female would 

 apparently show but twenty-two chromosomes; but even if this 

 be so the two members must separate again when transferred to 

 the male. 



In regard to Pyrrochoris, there is little doubt that the determina- 

 tion of the female number by Henking and Gross as twenty-four 

 was correct; and since the idiochromosome in the male is the 

 largest of the chromosomes we may expect the female groups to 

 show two such chromosomes.^** 



I should state the expectation less confidently in the case of Syro- 

 mastes if it stood entirely alone; but another case has now been 

 made known in which the male and female groups differ by more 

 than one chromosome. This occurs in the genus Galgulus, which 

 has been worked out in my laboratory by Mr. F. Payne (whose 

 results are now in press)" on material collected by myself. The 

 following facts are very clearly shown in this form. The sperma- 

 togonial number is thirty-five, the female number thirty-eight. 

 In the second division five of the chromosomes are always asso- 



^^ Henking's figures ('92) give considerable evidence that such is really the case. His Fig. 83 of 

 the first polar metaphase shows one of the twelve bivalents fully twice the size of the others; and the 

 same is true of Fig. 68, which shows a side view of the second polar spindle, though not all the chromo- 

 somes are shown. With this accords his Fig. 39 of a double group from a connective tissue cell of 

 the female showing forty-eight chromosomes, of which four, of nearly equal size, are nearly twice the 

 size of the others. This agrees precisely with the relation shown in a double group of Anasa figured 

 by me in a former paper ('06, Fig. 2, k) which shows twice the normal number of both the largest and 

 the smallest chromosomes. 



*' Since published in Biol. Bull., xiv, 5. 



