70 DEVELOPMENT OF 



occupied by the germs of the Cercarice in the *' nurses^ 

 themselves, and it cannot be doubted that the germs are 

 always collected in that situation as in a distinct organ 

 {uterus F), and that by the development of these germs 

 into embryos and the growth of the embryos, this organ 

 is enlarged, and consequently the whole cavity of the 

 body of the " nurse" distended and filled. In the same 

 way that the Cercaria within the " nurses' attain their 

 full development only by degrees, the " nurses' also 

 within their parents do not reach their full growth simul- 

 taneously, whence it must be assumed, that they, like the 

 Cercarice, are not all born at once. The series in the de- 

 velopment of the " nurses' from perfectly spherical germ 



granules is represented in figs. 3 a 3 p, and will 



afibrd when compared with the development of the Cer- 

 cari(B given above, and notwithstanding then' great re- 

 semblance, evident signs by which it may readily be 

 determined from the appearance of the embryo itself, 

 whether a Cercaria ox a " nurse" ialtrix) is about to be 

 formed from it. 



That the oral orifice and the head of the " nurses' and 

 ** parent nurses" are identical with the parts of the same 

 name in the Cercarice ; that the constitution of the collar 

 is the same in all three forms or generations ; that the 

 lateral processes of the " nurses" and '' parent nurses" are 

 the projecting borders of the posterior part of the body, 

 on each side of the root of the tail in the Cercarice ; and 

 finally, that the tail, although the Cercarice lose it, is also 

 the same organ in all three generations, are points to 

 which I surely need scarcely direct attention ; and all con- 

 jectures,* as to whether or no either the whole of the 

 " nurse" or ^^ parent nurse" or some of their organs, 

 may have a diff'erent object, must in my opinion cease of 

 themselves. 



We have thus followed the Bistoma to its third stage 



* As, for instance, the common opinion among the Gennans that the 

 " mirses" are only vitalized generative organs; Siebold's supposition that the 

 lateral processes may possibly perform the function of organs of nutrition, &c. 



