Katharine Foot and E. C. Strobell 233 



vesicle had brolcen down and its contents scattered tliroughout the cyto- 

 plasm. These structures in AUolohophora resemble some of the asters in 

 Cerebratitlus which Kostanecki interj^rets as expressions of a pathological 

 condition. They show, however, no evidence that they have originated 

 by division of the normal aster as Kostanecki, '02, interprets those of 

 Cerehraiulus, they indicate rather that their irregular dense centers are 

 small aggregations of dispersed nuclear substance, around which cyto- 

 plasmic rays focus. 



Mead gives no account of the development of the nine chromosomes* 

 which he finds in the first maturation spindle. These stages are omitted 

 also in Wheeler's work on Myzostoma, '97, where he first figures the 

 chromosomes as 12 tetrads suspended in the chromatic network of the 

 germinal vesicle. These are composed of two rods swollen at their 

 ends, and of these Wheeler says : " I have not studied the origin of the 

 double rods in the germinal vesicle so that I am unfortunately unable 

 to pass an opinion on the nature of the division in the fii'st spindle. In 

 the case of the second spindle, however, I feel confident that there is a 

 longitudinal splitting of each of the single chromatin rods remaining in 

 the egg after the formation of the first polar body" (p. 51). AUoloho- 

 phora supports Wheeler's observations as to the occasional persistence of 

 part of the membrane of the germinal vesicle until the spindle is formed 

 (cf. Photos. 84 to 87, Plate Y, wdth Wheeler's Fig. 63). In Myzostoma 

 the two centrioles are first seen near the membrane of the germinal 

 vesicle and in close relation to each other, being " connected by a delicate 

 achromatic bridge." Wheeler's Figs. 3 to 5 demonstrate the gradual 

 separation of these centrioles to form the poles of the first spindle. 



December 1, 190-1. 



PAPERS REFERRED TO. 



AxcEL, P., '02. — Histogenese et structure de la glande hermaphrodite d'Helix 



pomatia (Linn.) Arch, de biologie, Tome XIX. 

 Blackmax, M. W., '03. — The Spermatogenesis of the Myriopods. On the Chrom- 

 atin in the Spermatocytes of Scolopendra heros. Bio. Bull., Vol. V., 



No. IV. 

 BovERi, Th., '88. — Zellen-Studien. Jena. 

 ■ 02. — Ueber mehrpolige Mitosen als Mittel zur Analyse des Zellkerns. 



Vehr. d. phys. Med. Ges. Wixrzburg., N. F., Bd. XXXV. 

 Bryce, Thos. H., '01. — Maturation of the Ovum in Echinus. Quart. Journ. 



Mic. Sci., Vol. XLVI. 

 Calkins, Gary N., '95. — The Spermatogenesis of Lutabricus. Jour. 



Morph., XI. 

 CoE, Wesley, R., 'gg. — The Maturation and Fertilization of the Egg of Cere- 



bratulus. Zool. Jahrb., Bd. XII. 



