May, 1906.] A Reducing Division in Ascaris. 525 



Literature Cited. 



With two exceptions, I have hsted only the papers directly 

 referred to in the text. The exceptions are Guyer's extremely 

 important work published before the rennaissace of Mendel's 

 Law, which have not received from writers on kindred subjects, 

 the attention they deserve. 



1. Berghs, Jules. La Formation des Chromosomes Hetero- 



ty piques dans la Sporogenese Vegetale. II Depuis la 

 Sporogonie jusqu'an Spireme Definitiv. La Cellule 21 : 

 383-397 PI. 1. 1904. 



2. Brauer, a. Zur Kenntniss der Spermatogenese von 



Ascaris megalocephala. Archiv f Mik. Anat. u. Entw. 

 42 : 168. 1893. 



3. Gregoire, Victor. Les Resultats Acquis sur les Cineses de 



Maturation. Premiere Memoire: Revue Critique de la 

 Literature. La Cellule 22 : 221-376. 1905. 

 Material cited at p. 330. 



4. Guyer, M. F. Spermatogenesis of Normal and Hybrid 



Pigeons. Chicago, 1900. 



5. . Hvbridism and the Germ-Cell. Univ. Cincin- 

 nati. Bull. 21. 1902. 



6. Montgomery, Thos. H. Some Observations and Consider- 



ations on the Maturation Phenomena of Germ Cells. Biol. 

 Bull. 6 : 137. 1903. 



7. MoszKOWSKi, Max. Zur Richtungskorperbildung von As- 



caris megalocephala. Archiv f. Mik. Anat. u. Entw. 59 : 

 .388. 4 fig. 1902. 



8. Tretjakof, D. Die Bildung der Richtungskorperchen in 



den Eieren von Ascaris megalocephala. Archiv. f. Mik. 

 Anat. u. Entw. 65 : 3.58-.583. PI 21. Die Spermatogen- 

 ese bei Ascaris megalocephala. p. 383-435. PI. 22, 23. 

 fig. 1. 1905. 



Explanation of Plate XXXIII. 



The figures were drawn with a Leitz 1-16 oil immertion ob- 

 jective and a Bausch and Lomb 1-2 in. ocualr. They were draw^n 

 with the aid of a camera lucida and are reproduced 2-3 their 

 original size. 



Fig. 1. A nucleus just passing from the resting stage. The nuclear 

 membrane is extremely faint, being on the verge of disappearance. 



Fig. 2. The chromatin network well broken up and on the way to 

 the formation of the continuous spirem. 



Fig. 3. A continuous spirem. This is wrapped so tightly that it is 

 not possible to be certain all the strands run exactly as drawn. The nuc- 

 leus was, however, in this stage and about as drawn. 



Fig. 4. Slightly later than the last, showing the first appearance of 

 doubled granules on the still single linin spirem. As in fig. 3, the spirem 

 is too complicated to be followed with certaintv but it in the main as 

 represented. 



