240 Robert Wilhelm Hegner. 



producing four binucleated cells ; then the nuclei in these four cells 

 each divided producing four quadrinuclcated cells, two of which then 

 moved to either side of the body. No further change took place 

 within the two germ-glands until the time of hatching. Their posi- 

 tion was altered by the contraction of the ventral plate and, in the 

 young larva, they lay in the ninth abdominal segment level with the 

 union of the mid- with the hind-intestine. Each germ-gland now 

 acquired an epithelium of flattened cells. The testes could, at the 

 end of embryonic life, be distinguished by their narrowness, at- 

 tenuated ends, and many celled constitution, from the ovary, which 

 was broad, obtuse, and composed of only a few large cells. One of 

 ]>albiani's conclusions was that "les giandes genitales des deux sexes 

 out une origine absolument identique, naissant de la meme substance 

 et au meme point de I'ocuf." 



Cliironomus was also studied by Jaworowski (1882). This author 

 Avas led to believe that the germ-glands of insects developed from a 

 single mother cell, which gave rise by division to daughter cells, 

 these in turn became mother cells and produced daughter cells. In 

 this way the ''Kammern," "Endfaden" and "Ausfiihnmgsgang" 

 were all supposed to have arisen. 



Three papers record the results of Schneider's (1885) observa- 

 tions "iiber die Anlage der Geschlechtsorgane der Insecten." Al- 

 though his work was done chiefly on Chironom/ns plumosus, C plumi- 

 cornis, and a viviparous Cecidomyian, nevertheless he has made 

 the following unique generalization : "Die erste Anlage der Ge- 

 schlechtsorgane der Insecten besteht, soweit ich dicselbe verfolgt habe, 

 in einer Muskelfaser, welche sich von einem Fliigelmuskel abzweigt. 

 Sie sitzt also vorn und hinten an der Hypodermis. In der Mitte 

 derselben entsteht eine Anhiiufung von Iverncn durch Avelche die 

 Muskelfaser erst spindelformig, dann eiformig aufschwillt. Wir 

 wollen sie als die Geschlechtsanlage bezeichnen." 



Kowalevsky (1886) observed in Musca that the division of the 

 cleavage nucleus into two took place near the pointed end of the 

 Q^^. The nuclei produced by these two reached the posterior end 

 first and formed pole-cells which entered the cavity between the egg 

 and the yolk membrane. The further history of these cells was not 

 followed. 



