﻿140 William S. Marshall and Paul H. DernehL 



for numerous insect eggs. There are never in this stage as many 

 nuclei at the surface as later there are blastoderm cells. This in- 

 crease in number occurs by the division of the nuclei within the 

 Keimhantblastem and also later by a division of the blastoderm cells, 

 the former method lasting but a short time and resulting in the nuclei 

 being evenly distributed throughout the Keimhantblastem (Fig. 33). 



The arrival of the cleavage nuclei at the periphery of the egg 

 has been described very many times, it has been found that, among 

 different insects, there is a great Variation as to that part of the 

 egg at which the nuclei first arrive. To give an idea of this Varia- 

 tion we tabulate most of the results. 



Nuclei arrive at all 

 parts of egg's sur- 

 face at the same 

 time. 



At the posterior end 

 first. 



At the anterior end 

 first. 



Blochmann, for 



BOBRETZKY, for 



Heymons, for 



Noack, for 



Voeltzkow, for 



Weismann, for 



Ganin, for 



Gräber, for 



Grimm, for 



Heider, for 



Heymons, for 



KOWALEVSKY, for 



Weismann, for 



Ayers, for 



BOBRETZKY, for 



Bütschli, for 

 Carriere and 



Bürger, for 



Dickel, for 



Grassi, for 



Kowalevsky, for 



Weismann, for 



At the equator first. 



At the ventral surface 

 first. 



Appearing at surface 

 in groups. 



( Kulagin, 

 1 schwartze, 

 | Heymons, 

 l Melnikow, 



i Brandt, 



for 

 for 

 for 

 for 



for 



Biptera (Musea). 

 Lepidoptera (Porthesia) 

 Forficula. 



Diptera (Calliphora). 

 Coleoptera (Melolontha). 

 Diptera [Chironomus). 

 Hymenoptera [Formica) . 

 Diptera [Lucüia). 

 Diptera (Chironomus). 

 Coleoptera (Hydroplüliis). 

 Orth op tera ( GryUus) . 

 Diptera (Mnsca). 

 Hymenoptera. 

 Orthoptera (Oecanthus). 

 Lepidoptera (Pieris). 

 Hymenoptera (Apis). 



Hymenoptera ( Chalicodoma). 

 Hymenoptera (Apis). 

 Hymenoptera (Apis). 

 Hymenoptera (Apis). 

 Diptera (Musea). 

 Hymenoptera (Platy gaster). 

 Lepidop tera ( Lasioca mpa ) . 

 Orthoptera ( Gryllotalpa). 

 Coleoptera (Donacia). 



Odonata ( Callop teryx) . 



