ACCOUNT OF THE PHASMIDAE, WITH NOTES ON THE EGGS. 



79 



the capsule. In this membranous stage the micropylar area is quite distinct on the 

 endochorion and exhibits a very similar shape to that seen in the completed egg. 



The exochorion subsequently becomes hard and very perfectly attached to the 

 endochorion. It differs in the egg of every species I have examined, being in some 

 cases very thick (Leuckart says 1/6 of a millimetre in Cyphocrania violascens), but 

 in other species it is quite thin (Gigantophasma). This secondary product is very 

 vegetable- like. 



The vitelline membrane is free from the endochorion except at the micropyle, 

 where the two are firmly connected ; another striking peculiarity of this membrane 

 is that it is considerably thicker under the operculum than it is elsewhere. 



Capitulum. This peculiar structure, placed on the middle of the operculum, is 

 present in the eggs of the majority of species of Phasmidae but is entirely absent 

 from others. It differs in every species, but when present is always a well-developed 

 structure, and there are, so far as I know no forms in which it is present in an 

 atrophied or rudimentary state; it is always either well developed or entirely absent 1 . 

 It consists of two parts, one of which is truly a part of the operculum ; the 

 capitulum itself is a less rigid body, superposed on the operculum and sometimes nearly 

 concealing it (PI. IX, Fig. 31). The part continuous with the operculum may form a 

 stalk more or less elongate, and then projects to a greater or less extent into the soft 

 body or capitulum proper, to which it forms a sort of core. The capitulum is present at 

 an early stage of the formation of the egg, and if the half-grown egg of Anchiale 

 confusa (Fig. 30) be looked at in the egg-tube it appears as if the capitulum is 

 another less-grown egg attached to the larger egg. I think this will prove to be 

 really the case and that the capitulum proper will be found to be the contents of 

 another egg-chamber that have become subsidiary to the larger egg. 



The species known to me in which the capitulum is entirely wanting are 

 Brachyrtacus celatics, Eurycantha horrida, and Hermarchus pythonius (Figs. 32, 36, 41). 

 I believe that the capitulum is also absent in the egg of Acanthodyta spiniventris, 

 but this is not certain, as I speak only from my recollection of a single much damaged 

 egg of which the operculum is now lost. 



No function can be assigned to the capitulum in its formed state. It has, as 

 was pointed out by Leuckart, no connection with the micropyle apparatus ; it is not 

 adapted to facilitate the admission of air to the egg, but must rather prevent such 

 access. If it discharge any important function this is probably confined to a 

 comparatively early period of the growth of the egg. 



Operculum. This structure is present in all the known eggs of Phasmidae ; it 

 is a lid that fits very accurately to the truncate anterior extremity of the egg ; its 

 margin is surrounded by the margin of the capsule, and it is owing to the perfect 

 fit between the two that the operculum retains its position. In the completed egg 

 the operculum has no continuity with the capsule proper, neither have I been able to 



1 The egg of Oyphocrania violascens as figured by Leuckart, 1. c. pi. x. figs. 19, 20, exhibits a small 

 knob on the middle of the operculum. I think this is not a capitulum. The only mention of Cyphocrania 

 violascens made by Westwood in his Catalogue of Phasmidae is as a synonym of Acrophylla violascens; 

 this has been since referred by Stal to Tropidoderus, an insect now considered but distantly related to Cypho- 

 crania. I do not know this insect or its egg. 



