THE EMBRYOLOGY OF THE HONEY BEE 13 



and scattered in sections of ova fixed in acetic alcohol, and absent 

 in those fixed in Petrunkewitsch's fluid. So far all the elements 

 seen in the fresh egg have been accounted for except the tiny 

 greenish bodies embedded in the protoplasm (4). These seem 

 to be represented by deeply stained minute granules, which indeed 

 appear to lend to the protoplasmic network its dark appearance. 



In addition to the structural elements above mentioned, there 

 are visible in the anterior end of the egg one or more irregular 

 island-like masses composed of the same granular protoplasm as 

 the network, the cleavage cells (Figs. I and 5 CC). Each of 

 these possesses a clear spherical nucleus. At the close of the 

 process of fertilization there is of course but one nucleated cell, 

 whose nucleus (first segmentation nucleus) arose by the union — 

 in the fertilized egg, — of the nuclei of the egg and the sperm 

 (male and female pronuclei). 1 This cell soon gives rise by 

 mitotic division to a group of daughter cells, four of which are 

 more or less plainly visible in the figure. The form of the cleav- 

 age cells is highly irregular, or amoeboid, their outlines indented 

 by concavities which represent the imprint of the vitelline spheres. 

 Between the indentations arise processes of irregular shapes 

 which stretch out into the surrounding cytoplasmic network and 

 are continuous with it. These cells will be considered at greater 

 length in the next section. 



An extended review of the various accounts of the organiza- 

 tion of the eggs of other insects is not possible here ; moreover a 

 survey of these accounts, as well as of the statements in the text- 

 books, suffices to show that they quite uniformly agree in de- 

 scribing the contents of the insect egg as composed of the 

 following morphological elements : ( 1 ) A protoplasmic mesh- 

 work, which in many insects is extended over the periphery of the 

 egg to form a cortical layer ; in others this layer is absent. In the 

 protoplasm are also included the segmentation nucleus or its 

 products. (2) Yolk bodies, generally in the form of balls or 

 spheres, enclosed in the meshes of the protoplasm. (3) Fat 

 globules. (4) Minute rod-like or rounded bodies embedded in the 

 substance of the protoplasm, and present only in certain insect 

 eggs. These bodies were discovered and described by Bloch- 



1 For an account of this process in the honey bee, see Blochmann (1889), 

 Petrunkewitsch (1901, 1902), and Nachtsheim (1913). 



