No. 520] 



NOTES AND LITERATURE 



251 



locephala bivalent would have six (6) chromosomes in the female 

 and five (5) in the male (apparently four (4) in each since 

 the heterochromosomes commonly couple with the ordinary 

 chromosomes). 



The attempt to rationalize the assumption of such a union 

 involves the hypothesis of chromosome individuality in extreme 

 form, viz: "We can not doubt that also in the apparently homo- 

 geneous nucleus of the spermium each chromosome preserves 

 its individuality: hut all are most closely pressed together" (p. 

 139). The greater effort here demanded (as compared with the 

 egg pronucleus) to separate the chromosomes in this more com- 

 pressed condition affects also the odd chromosome and frequently 

 disjoins it from its ' ' companion. ' ' 



Thus two more forms (from the group of the Nematodes) are 

 shown to conform to Wilson's scheme of sex-determination. 

 And though Boveri is forced to retract (p. 137) his former state- 

 ment regarding a preponderance of chromatin in the female 

 sea-urchin as judged from Baltzer's plates the evidence accumu- 

 lates that the female sex is somehow associated with a greater 

 amount of chromatin. 9 



In an extensive paper of 110 pages on sex-determination in 

 Polyps, Nussbaum 10 describes in detail a large series of experi- 

 ments extending from 1891 to 1897 on Ilxjdra grisea. His dis- 

 cussion of results involves comparisons with the works princi- 

 pally of Krapfenbauer (H. fusca), Frischholz (H. fusca and H. 

 grisea), Whitney (H. viridis) and Annandale orientalis). 



The aquaria were all arranged under similar conditions of 

 light and heat ; only the nutritive conditions were caused to vary 

 by changes in the amount of food supply and by induced periods 

 of budding. The temperature is said to have an effect on sex 

 only indirectly through influence on the nutrition. In contra- 

 distinction to the four above-named investigators, Nussbaum 

 maintains that the nutrition and not the temperature is the chief 

 factor which determines change from the asexual or budding 

 condition to the sexual (dioecious and hermaphrodite) ; though 

 he agrees with the latter two that for each species there is a 

 definite temperature-optimum. 



• The case of Acholic multispinoa described by Payne (Biol Bull, Vol. 

 16, nos. 3 and 4, 1909) may perhaps prove a real exception, though it may 

 be harmonized, as Payne suggests, by assuming a greater combined activity 

 for the several smaller "differential chromosomes," than for the single 

 absolutely larger male member. 



,,. x.^l.m:;,!. V.. " IVi <:. - ^l-^.il.iu: i ■ i P 'y: ■ • .•■ A-rh 

 (Pfliiger) f. Physiologie, Dec. 30, 1909, Bd. 130. 



