ON THE OVIPAROUS SPECIES OF ONYCHOPHORA. 381 



undergoes a certain amount of wrinkling-, probably in drying, 

 and the wrinkling gives rise to the extremely characteristic 

 surface pattern or sculpture to which I called attention (cf. 7) 

 long ago, and samples of which are shown in figs. 28 and 24. It 

 will be seen that the pattern is not quite identical in all cases, 

 the differences, doubtless, depending upon the thickness of the 

 outer layer and the particular conditions under which drying 

 takes place. 



The views expressed above as to the formation of the 

 chorion in Ooperipatus oviparus differ to some extent 

 from my previously expressed ideas on the subject, but 

 the question is an extremely difficult one, and cannot even 

 yet be regarded as by any means finally settled. We 

 may, however, now regard it as certain that the chorion 

 consists of two layers, an inner thick and radially striated 

 layer, and an outer clear layer which is thickened over 

 certain areas to form mound-like protuberances. The fully 

 formed chorion is a tough, flexible membrane, varying in 

 thickness up to about 0'04 mm. (exclusive of protuberances). 

 When newly laid it has a pale yellow colour, but preserved 

 specimens may become much darker, and the deposited 

 eggs darkened greatly in course of time. 



In Ooperipatus viridimaculatus the chorion certainly 

 has a structure very similar to that exhibited by 0. 

 oviparus. I have observed stages corresponding to B and 

 C of the former, B in the oviduct and C after deposition. 

 In the former I was unable to detect the radial striation 

 in the very thick inner portion, but the rounded protuber- 

 ances on the outside were quite distinct. In the latter 

 (figs. 32, 33) the radial structure was indicated by the 

 strong tendency to split up radially which the chorion 

 manifested on compression. The rounded protuberances 

 on the outer surface had become to some extent wrinkled 

 (fig. 32), but not to the same degree as seems to be usual in 

 0. oviparus. It must be borne in mind, however, that only 

 a single egg of 0. viridimaculatus was observed after 

 deposition, and that may possibly have been prematurely 



