96 THE BUTTERFLIES OF NEW ENGLAND. 



It is a law in this world that all things have a lowly origin. The evo- 

 lution of all living beings from simple unicellular germs is an established 

 fact of science. The egg is generally looked upon as the simplest condition 

 of the animal. At least in insects, however, there seems to be an earlier 

 and simpler condition than is found in the egg. Here we should make 

 the primitive egg cell in the terminal chamber of the ovariole, or in the 

 primitive ovary before the ovariole is developed, the starting point in the 

 study of embryology. This idea may be objected to on the ground that 

 the egg cell is not complete until after the reception of the male element, 

 and that only after that is accomplished do we have a cell capable of 

 reproducing the species. The force of such an objection is more apparent 

 than real when one recollects that in some insects, notably in the saw-flies 

 and the honey-bee, eggs develop without the help of the male element. 

 The eggs of some insects (viviparous plant-lice) are incapable of leading 

 an independent existence and continue to receive food and grow. 



The ovary of an insect is at first a simple mass of similar cells, originat- 

 ing as described below and remaining for a more or less extended period 

 of time apparently without change, except that it becomes surrounded by 

 an investment of connective tissue. The cells are now said to fuse so as 

 to form a syncytium, but this I am inclined to doubt ; indeed some studies 

 on which I am engaged on other insects give me every reason to 

 doubt it, though a few of the critical stages are still unknown to me. The 

 evidence is this : the oldest ovary in which the ovarioles are not yet 

 developed still consists of distinct cells, and the youngest ovariole known 

 to me has in the lower end of the end-chamber far more distinct egg cells 

 than enough to account for all the eggs that can be subsequently devel- 

 oped by that ovariole. The upper end of the end-chamber may be a 

 syncytium and in some of the older ovarioles of some insects the whole 

 end-chamber seems to be 'converted into one, but this appears to be a 

 secondary condition. It is a point worthy of attention in studying the 

 ovarioles of insects, that before the largest egg has attained any consider- 

 able size all the cells that produce eggs have been differentiated enough to 

 be certainly recognized as egg cells. The study of the earliest stages of 

 the egg must be carried on in the larval and pupal stages and not in the 

 adult insect. 



Besides the cells that go to make u\) the syncytium there are three kinds 

 of cells in the ovariole of the group of insects to which Euvanessa belongs, 

 the egg cell proper, the epithelium cells and the nutriti^'e cells. They are 

 all derived from the indifferent cells of the primitive ovary and are homolo- 

 gous structures. When the butterfly emerges from the pupa the ova- 

 rioles are already quite well developed. They consist of long slender 

 filaments made up by the repetition of an oval unit, the egg chamber ; 

 these eo-g- chambers constantlv diminish in size towards the end-chamber 



