THE CHROMOSOMES OF ACHOLLA MULTISPINOSA.^ 



FERNANDUS PAYNE. 



In a recent paper entitled " Some New Types of Chromosome 

 Distribution and their Relation to Sex," I described in part the 

 history of the chromosomes in Acholla iimltispinosa. At that 

 time, I had but little material and was unable to say with certainty 

 just what occurred in the second maturation division. However, 

 I stated that all the evidence pointed to the conclusion that the ten 

 chromosomes in the ring divided equally while the members of 

 the hexad group in the middle remained undivided, five of them 

 passing to one pole, and one to the other. I also stated that the 

 number of chromosomes and their size relations in the male and 

 female somatic cells made it almost conclusive how the members 

 of the hexad group separated ; that no other manner of distribu- 

 tion could give an end result of 26 chromosomes for the male 

 and 30 for the female. 



In order to clear up the doubtful points, I collected new ma- 

 terial in larger quantities during the past summer and fortunately 

 have been able to follow the complete history of the chromosomes 

 in the spermatogonial, oogonial and the first and second matura- 

 tion divisions. As a result, I can state that my former observa- 

 tions were entirely correct and that my inference in regard to the 

 separation of the chromosomes in the second division has proven 

 true. 



The oogonial divisions (Fig. i, A, B, C and D) show 30 

 chromosomes, 24 of which are approximately the same size while 

 six are much smaller. I have examined female material from 

 New Jersey, New York, Indiana and Illinois and they all show 

 the same number and size relations. The spermatogonial groups 

 (Fig. I, E, F, G and H), on the other hand, contain 26 chromo- 

 somes, 22 medium sized, one very large and three small. Since 

 the number and size relations of the chromosomes in the male 

 and female groups are so different, it might be argued that I have 

 been working with two species. In regard to this question, I 



1 Contribution from the Zoological Laboratory of Indiana University, No. ill. 



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