224 First "Maturation Spiiullc of All()l()!)0])liora Fretida 



criterion of the synapsis stage." The photographs of our Plates VII and 

 VIII demonstrate that in AUoIohophora "it is a case of chromosomes 

 already closely connected remaining so." 



Many of our photographs confirm A. and K. E. Schreiner's, '04, obser- 

 vations on the spermatocytes of Myxinc r/lutinosa and Spinax niger. The 

 delicate thread-like reticulum in the early prophase (cf. Fig. 2 with our 

 Photo. Ill), the coarse spireme of the later stage (cf. their Figs. 3, 5 and 

 23 with our Photos. 114 and 115, Plate VII), and finally the form of the 

 bivalent chromosomes. The rings, figures 8, etc., of Schreiner's Fig. 15 

 are reproduced in Allololiopliora, though in their mode of formation and 

 subsequent division there are fundamental differences. They interpret 

 the first furrow of the spireme as due to a union 'of two of the delicate 

 threads of the earlier stage, and at a later stage they identify a second 

 longitudinal split of the spireme, these two longitudinal divisions indi- 

 'cating'the method of separation of the chromosomes for the first and 

 second divisions. The individuals of each bivalent chromosome are 

 paired longitudinally in the spireme, whereas in Allolohopliora they are 

 placed end to end, thus though the rings, figures 8, etc., of Schreiner's 

 Fig. 15 and those of Allolohopliora are formed alike by the uniting of 

 the ends of two univalent chromosomes, they have attained this final 

 .arrangement by an entirely different method. In both forms, therefore, 

 the first division separates univalent chromosomes, though in one case 

 the division is longitudinal and in the other transverse. 



This transverse division of the chromosomes supports Lillie's, '01, 

 observations on Unio. He says, " The first division is certainly at right 

 angles to the long axis of the chromosomes, as these lie in the equatorial 

 plate," p. 236. 



The spireme demonstrated in our photographs of Plate VII and the 

 "''' heterotypic " chromosomes of Plate IX confirm Flemming's obser- 

 •vations on the spermatocytes of Salamandra maculosa published in 1887. 

 "The "heterotypic" chromosomes of his Figs. 22, 23 and 25 are accurately 

 Teproduced in several of our photographs of Plate IX. Since the ring 

 ■chromosome was demonstrated by Flemming many investigators have 

 identified them in a variety of forms. The ring chromosomes of our pho- 

 tographs of Plates VIII and IX are similar to those demonstrated by 

 Henking," '91, in Pyrrliocoris ; Moore, '95, in Elasmobranchs; Bolles Lee, 

 '97, in Helix; von Klinckqwstrom, '97, in Prostheceraeus, de Sinety, '01, 

 in Orthoptera, Schockaert, '04, in Thysanozoon and Montgomery, '04, in 



^^ Henking interprets the first division as a reducing division and the second 

 as an equation division. 



