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William S. Marshall and Paul H. Dernehl, 



of the egg, are represented as separated from eacb other by boun- 

 daries tbus giving to each separated part tbe appearance of a cell. 

 Two of tbe nuclei with surrounding cytoplasm are figured enlarged, 

 eacb nucleus having in its center a large irregulär spot (nucleole). 

 Huxley says: »Tbe peripberal clear layer is, on tbe other hand, in 

 all essential respects, comparable to a blastodermic vesicle; and I 

 see no reason wby it sbould not be called a blastoderm.« This 

 blastoderm becomes two layered. Huxley tbougbt that tbe »pseudo- 

 val endoplast« (nucleus) divided and gave rise to endoplasts of the 

 gern; or, in other words, the nuclei of the blastoderm cells came 

 from the nucleus of tbe egg (first segmentation nucleus). 



The following year Leückart (37), in giving the development 

 of Melophagus , describes the yolk as withdrawing from tbe cell 

 membranes leaving a clear space filled with fluid, which was largest 

 at the poles. The »egg-nucleus« be lost sigbt of but saw in the 

 egg a number of clear bladder-like spots. He disagrees with Zad- 

 dach (63) who called tbese spots nucleated cells, and held that they 

 later formed the blastoderm. These »cells« were at first few in 

 number and far apart, but occurring in some eggs in greater num- 

 bers than in others. Leückart observed some of these dividing, 

 and then goes on to declare that they are not cells, »sondern viel- 

 mehr Körper, die den Zellenbildungsprozeß erst einleiten«. He did 

 not observe the origin of the blastoderm cells, but tbought they came 

 from the »egg-nucleus« by a process of budding. According to 

 Leückart the blastoderm was but one layer in thickness. He com- 

 pares the segmentation of tbe insects egg with that of other animals, 

 and describes it as a sort of superficial segmentation. 



A number of brief observations on insect's eggs made by 

 Rathke (47) were gathered by Hagen and published in 1861. Rathke, 

 in Naucoris, observed the blastoderm cells, but was unable to teil if 

 they surrounded the egg or were present in groups upon its surface. 

 Each cell contained a spherical nucleus and one to two nucleoles. 

 He also described the egg of a beetle as having a clearer layer on 

 the periphery in which were a number of blastoderm cells. The 

 egg of Liparis was described as having this same peripberal mass 

 and containing more than a Single iayer of cells. In Phryganid eggs 

 he noticed the same layer, »Embryonal Substanz«, but not so evenly 

 distributed over the egg; he here also noticed that the ventral sur- 

 face developed first. The next year Robin (48, 49) observed a num- 

 ber of half round bodies in the egg of Tipulaires, which became 



