223 First Maturation Spindle of iMlolobophora Foetida 



ation spindle of Cymbulia, Fig. 7, though he interprets their division as 

 longitudinal. 



This egg agrees with the observations of the many investigators who 

 have demonstrated for both oocytes and spermatocytes a marked differ- 

 ence in the size of the chromosomes of the first spindle. In Crepidula, 

 Conklin, '02, has shown this inequality to have reached the ratio of one 

 to fifteen in volume. In Allolohophora the inequality in the size of the 

 chromosomes is distinctly seen at the prophases and metaphase ; compare 

 the two chromosomes in the same germinal vesicle of Photos. 51 and. 52, 

 Plate III, and chromosomes in the germinal vesicle of Photo. 116, Plate 

 VII, and those of Plate VIII. Compare the size of the chromosomes in 

 the first i^pindle (metaphase) Photo. 33, Plate II, and. those of Plate IX. 



It is more difficult, however, to demonstrate a persistent and individual 

 form for each chromosome and in fixed and sectioned eggs we have found 

 this quite impossible. For example, in a collection of thirty-four photo- 

 graphs showing every chromosome in four first spindles at the meta- 

 phase it was impossible to identify any one chromosome in the four 

 spindles as the same individual. This is undoubtedly due in part to 

 distortion of normal forms by fixation and as a rule the chromosomes are 

 so closely massed in fixed material that their individuality is obscured 

 (e. g.. Photos. 69 and 70, Plate IV, 85 to 89, Plate V). In dried germ- 

 inal vesicles this massing of the chromosomes is avoided and individuals 

 can be distinctly differentiated. Although the individuality of these 

 chromosomes is not sufficienth^ pronounced to admit of a definite identifi- 

 cation of the individual at each stage, a comparison of the chromosomes 

 of the prophases of Plate VIII with those of the metaphase on Plate IX 

 will demonstrate that a few of the individual chromosomes of the pro- 

 phases can be identified in the metaphase with some accuracy, and this 

 argues strongly for the individuality of all, and supports the theory which 

 has been so frequently and ably defended by Boveri." 



The prophases of the first spindle of Allolohophora as above demon- 

 strated confirm A'^om Path's interpretation of the prophases of the first 

 spindle of the spermatocytes of Gryllotalpha published in 1892. When 



'^ After our paper had gone to press Baumgartner's interesting article 

 appeared, giving " Some new Evidence for the Individuality of the Chro- 

 mosomes," Bio. Bull., Vol. VIII, 1904. Our Photos. 116 to 130, Plates VII, 

 VIII and IX demonstrate that Baumgartner's suggestive conclusions are not 

 supported by the egg of Allolobophora. We find no constant form differences 

 of the chromosomes, the simplest form of the bivalent chromosome is two rods 

 attached end to end, and these present a variety of shapes, rings, figures 8, 

 crosses, etc., without any regularity or constancy. The free ends of the 



