52 [August, 



transverse diameter is not diminished (rather increased, perhaps) in 

 the middle. Moreover, the grasping of the last half of the egg by the 

 finger-like appendages (and I have seen the flexible shell strongly in- 

 dented by their action) tends to force the contents towards the other 

 extremity, and so diminish the size of the last laid, which is also the 

 cephalic, end of the egg. These conditions are often persistent ; so 

 that I believe it may be possible to tell by them which side of the egg 

 looked ventrally, i. e., towards the surface of attachment, when laid, 

 and which end will contain the head of the future larva. 



When fresh laid, and enveloped in the glutinous matter, the eggs 

 are perfectly smooth, shining and opaque. The colour is a clear yolk- 

 yellow, varying a good deal in depth of tint in different individuals. 

 I had once two females laying in the same pot whose eggs I could 

 very easily distinguish in this way. There are often red ticks or short 

 hyphen-like lines scattered sparsely and without regularity over the 

 surface, like the markings on birds' eggs. I have seen a speck of this 

 red matter on the glutinous substance extending between two eggs and 

 not attached to either. 



The eggs should be kept in a moist atmosphere during incubation, 

 which preserves them plump and free from indentations, and greatly 

 facilitates the hatching-out of the larva?. I generally cut out the 

 piece of dock with the eggs upon it, and put it into a plaster-of-paris 

 tray covered by a pane of glass. The eggs may either be turned down 

 in the natural position, or up towards the light ; in any case, the 

 venter of the larva developes on the side that is uppermost, whether 

 that be the free surface of the egg or the surface of attachment.* 

 This result is the same when all the light and heat falling on the eggs 

 is made to reach them only from beneath, as I have proved by keeping 

 them over mirrors, while the upper surface was kept cool by evapora- 

 tion. It seems to be an affair of gravitation, as in the avian and 

 batrachian egg. As the mature larva escapes from the free surface of 

 the shell with the back of the thorax first, in those eggs which have 

 been kept in the reverse position, and in which the venter of the larva 

 has developed next the free surface, the young larva is obliged to make 

 a half revolution on its long axis within the shell, before it can burst 

 the latter and escape out of it. It tivists itself round, bringing into 

 view the abdominal spiracles in a spiral line and the four conspicuous 

 warts on the dorsum, to be presently described as the "thoracic 

 square." 



* This statement is only absolute for eggs laid evenly on a horizontal surface, and kept in the 

 same position throughout incubation. Even then, individual exceptions will be met with, as in the 

 still rarer case of the cephalic and caudal end* lying the contrary way.— J. A. O. 



