DEVELOPMENT OF NEMATOIDA. 291 



Even before the last-mentioned authors, some of the English 

 writers and Bischoff had ascertained that the segmentation of the 

 eggs of worms takes place and advances in various, even strong, 

 chemical fluids. 



The literature of this subject is as follows : ' Report to the 

 Royal Society of London on Nelson's Memoir upon Ascaris 

 mystax, made by Thompson, in May 1K51 •' Bischoff, ' Wiederle- 

 gung des von D. Keber bei den Naiden und D. Nelson bei den 

 Ascariden behaupteten Eindringens der Spermatozoiden in das Ei, 

 Giessen 1854;' and ' Bestatigung des von Dr. Newport bei den 

 Batrachiern und von Dr. Barry beim Kaninchen behaupteten 

 Eindringens der Spermatozoiden in das Ei, Giessen, 25th May, 

 1854,' with additions by Leuckart; Meissner, in Siebold and 

 Kolliker's ' Zeitschrift,' Band vi, p. 208 ; and Bischoff, in the 

 same journal, vi, 377 ; and, lastly, Thompson ' On the Seminal 

 Corpuscles, the Eggs, and the Fecundation of Ascaris mystax' 

 in Siebold and Kolliker's 'Zeitschrift,' viii, p. 425, in a letter to 

 Kolliker. 



To furnish the development of the creatures to be treated 

 of here in as connected a manner as possible, we shall, fol- 

 lowing the observers just mentioned, give a preliminary summary 

 of some things which properly belong to a subsequent place and 

 indeed to the special examination of the sexual organs. 



The first foundations of the ovigerous tube of the nematode 

 worms are formed, according to Kolliker, by the occurrence at the 

 extreme apex of the future tube of a series of cells, the contiguous 

 walls of which become dissolved, so that their communicating 

 cavities gradually run together to form the ovigerous tube, which 

 increases by new formation of cells at its apex. The production 

 of the lowest parts of the ovary is unknown, according to Kolliker. 

 I do not know whether the large globular cells which I found 

 throughout the middle of the body on both sides of the intestine 

 in a young immature Ascaris lumbricoides of 1| inches in length, 

 are those which, gradually approaching each other, become 

 amalgamated to form the generative sac, this would not be 

 improbable from their position. 



In the fully developed female organ (ovigerous tube), which 

 forms a long, simple, partially double or multiple tube, twisting 

 about the whole intestinal canal, we may distinguish, according 

 to Meissner, the following six parts : 



1. The Germ-stock (Eierkeimstock), is the exceedingly small 



