588 MALCOLM LAURIE. 



liarities of those organs with S. fulvipes. Duvernoy, how- 

 ever, deals only with the external appearance of ovaries in 

 which the development of the embryo had already advanced 

 some way. 



In Scorpio fulvipes the ovary agrees with that of 

 Euscorpius in its anatomy, in so far as it consists of a network 

 of tubes bearing a number of eggs which cause the tubes 

 to bulge at intervals into the body space. Beyond this, how- 

 ever, there are many important differences. The ovarian tube 

 in place of the large oval sessile ova of Euscorpius bears a 

 number of long diverticula, each of which ends in a solid 

 coiled appendix (fig. 1). These diverticula were described by 

 Duvernoy^ as the eggs, but the comparatively small egg occu- 

 pies only one tenth of the length of the diverticulum, and lies 

 at its distal end at the root of the appendix (fig. 1, ov.). 



The formation of these diverticula can be easily understood 

 from fig. 2, which shows a section of a young egg such as ov' 

 in fig. 1. The egg, which is formed as in Euscorpius by the 

 growth of one of the cells of the inner layer of the two-layered 

 ovarian tube, is carried out at the end of an outgrowth of the 

 ovarian tube, and is at first completely surrounded by a mass 

 of cells of the inner layer. At a stage somewhat later than 

 that in fig. 2 an opening is formed through these cells, so that 

 the ovum is only separated from the cavity of the diverticulum 

 by the vitelline membrane which surrounds it. There is no 

 specialisation of any of the cells for the purpose of forming 

 yolk, and in fact the egg is, when ripe, entirely without food 

 yolk. 



The whole diverticulum, as is seen in fig. 1, consists of four 

 distinct regions : — A long stalk {st), a thickened collar (c), a 

 somewhat conical portion in which the ovum lies {ov), and a 

 long appendix. The stalk is peculiar in that the continuation 

 of the inner layer of the ovarian tube is divided into two 

 distinct portions. The inner one (fig. 3, i.l.) next the lumen is 

 formed of a single layer of long cylindrical cells with their 



' Duvernoy, " Fragments sur les orgaues dc la Generation dc divers ani- 

 maux," ' Mem. de TAcad. Sci. de I'Institut,' t. xxiii. 



