of the Oca o/Chthonius. 201 



in the formation of the blastoderm ; this is surrounded by a 

 tolerably voluminous, finely granular layer of protoplasm. 

 The protoplasm layer is followed by an inconsiderable layer 

 of primaiy deutoplasm-drops, which again is surrounded by a 

 voluminous layer of the secondary deutopl asm-drops, " the 

 true nutritive vitellus." This stage is the last that I could 

 meet with in the interior of the female ; in a few specimens I 

 further detected an invagination of the nutritive vitellus at the 

 two poles of the ovum ; but it is certain that this stage repre- 

 sents an ovum ready for deposition. 



When the ova are ready for deposition they pass through 

 the pedicle (the cells of which, as in the true spiders *, are 

 not very perceptible, perhaps also in consequence of the 

 secreted deutoplasm-spheres ?) into the internal cavity of the 

 ovary. That in the Chernetidte, as in the Araneidge, the ova 

 do not really fall off from the pedicles, perhaps into the body- 

 cavity (as might be supposed with regard to the true spiders 

 from Leydig's t, and with regard to the Chernetidas from 

 Metschnikoff 's % figures) , but pass through the pedicle into the 

 oviduct, has already been observed by Menge §, whose inves- 

 tigations I can only confirm ; for an ovary dissected out of a 

 female which had already deposited her eggs was abundantly 

 beset with empty follicles. The oviducts opening in the 

 second abdominal segment may also serve to convince us of 

 this. The process of oviposition was observed by Leuckart || 

 in the Pentastomes 5 and as it is in general precisely similar to 

 that of CJithoniuSj we shall not occupy any more time with its 

 description. Metschnikoff If also observed this process in the 

 scorpions ; and in these also it resembles that of the Penta- 

 stomes. 



No doubt owing to his scanty materials, Metschnikoff did 

 not observe the very first metamorphosis preceding the deve- 

 lopment of the true nutritive vitellus ; and hence, of course, 

 the true origin of the vitelline spheres (which, as he remarks**, 

 are "so characteristic of Chelifer'''') escaped him. Otherwise 

 it is impossible that such great differences should occur in the 

 development of two genera of one and the same order. 



I must further remark that Metschnikoff might well state that 



* Bertkau, /. c. p. 246. 



t Leydig, * Lelirbuch der Histologie,' p. 550, fig. 271. 

 t MetschuikofF, " Entwickluno: des CheliferP I. c. pi. xxxviii. fis:s. 

 1&2. 



§ Menge, I. c. p. 17, pi. ii. fig. 10. 



II Leuckart, ' Ban und Entwickeluugsgeschichte der Pentastomen,' 

 Leipzig imd Heidelberg, 1860, p, 84. 



51 Metschnikoff, " Embryologie des Scorpions," /. c, pp. 208, 209. 

 ** Metschnikofi; " Entw. des Chelifer;' I.e. p. 514. 



