Manchester Memoirs, Vol. I. (1906), No. 6. H 



changes, his observations are of interest. In the early- 

 stages of the segmentation of the ovum, he describes and 

 figures ' Polzellen.' He traced these and found that they 

 underwent further subdivision and finally formed the 

 genital rudiment. Meinert (62) six years later investigated 

 the development of the same insect. He considered that 

 the ' Polzellen' were separated off from the layer of blasto- 

 derm cells, and disbelieves the idea that they wander 

 off later to form the genital fundament, although he 

 apparently did not trace their fate. The ' Polzellen ' may 

 not be the true polar bodies as is shown in the next 

 account of Chirononms. 



Chironomus. Balbiani (i) followed the 'globules 

 polaires' which are formed at the posterior end of the ovum 

 of this insect and traced them to the primitive germ cells. 

 Ritter (81) investigated the early embryonic development 

 of Chirojionms. He describes the true polar nuclei, which 

 apparently have no relation to the ' Polzellen,' they 

 disintegrate before the latter are formed, and lie in the 

 anterior region of the 0.%^. He traced the ' Polzellen ' to 

 the genital rudiments, and so confirmed Balbiani's conclu- 

 sions. Metschnikoffs conclusions as to the fate of the 

 ' Polzellen ' in Miastor were probably correct. 



From Ritter's observations it appears that the 

 Polzellen are in no way connected with the polar nuclei ; 

 they probably arise in the same way in Miastor, but the 

 subject needs reinvestigating. 



LEPIDOPTERA. 



A few cases of Tychoparthenogenesis, which occurs 

 in this group, have been investigated cytologically. Males 

 and females may be produced. The maturation of the 



