216 ENTOZOA. 



of tte development of the ova and embryos from their earliest 

 commencement. The outer membrane, according to the latter 

 authority, constitutes the primitive yelk-membrane, within which 

 a part of the yelk-contents separate to form the true egg and em- 

 bryo by a process of daughter-cell formation ; the other part of 

 the yelk remains as a granular mass, being concerned, possibly, as 

 an organ for secreting the true chitinous shell (Fig. 4, Plate ^11). 

 When the true sheU is fully formed and the outer layer is still in exis- 

 tence I have observed this granular mass to be altogether absent, 

 Weinland describes a second delicate or middle membrane within 

 the outer one (in Hymsnolopis), but this may be only the surface of 

 the coagulated contents, which, in addition to the well-defined 

 granular mass, consists of loose granules floating in a clear albu- 

 minous fluid. The true shell displays a series of radiating and cir- 

 cular hues ; the former, however, are more conspicuous than the 

 latter, being due, according to Leuckart, to the presence of a series 

 of fine rod-like chitinous elements, which are formed on the exter- 

 nal surface of the original true shell membrane. The enclosed 

 embryo presents a simple granular aspect, and is furnished with 

 six boring spines, arranged in three pairs, the whole being invested 

 by an extremely delicate skia-membrane, which is separated from 

 the inner surface of the shell by a clear transparent fluid. The 

 embryo measures j^" in diameter. 



Leaving the consideration of the measle as a disease for sub- 

 sequent notice, I now proceed to glance at the so-called scolex or 

 larval condition of this tapeworm, which in its most complete 

 stage of development constitutes the weU-known Gysticercus (telce) 

 cellulosce of authors. Its earlier stages of growth have been ably 

 worked out by Leuckart. In this kind of investigation, it is 

 true, he was anticipated by Eainey, but it may be reason- 

 ably doubted if the minute corpuscles described by Eainey as 

 representing " the earliest indication of this species of Gysticercus" 

 have anything to do with the measles whatever. It unfortunately 

 happens, also, that the so-called Raineyan sacs with their con- 



