XXVIU EXPLANATION OF TUE PLATES. 



/. The tliick-wullod peculiar sac. 



g. PyiiforiH sac, a receptacle for the ova. 



i. Male organs. 



The fi.nure also presents the arraiigcnK'nt of the dermal 

 spines, and the general form of the animal. 



Plate XI. page 482. 



Fig. 2. The anterior extremity and snctorial mouth of Neiironaia 

 monroii more highly magnified. 



Fig. 7. The cyst of Neuronaia monroii in a bundle of nervous fila- 

 ments. The fissured appearance of the cyst, Avith its epithelia, 

 is represented in this drawing. 



I am inclined to believe that the function of the cyst in 

 this and tlie other Cystic Entozoa is to sup])]y noiuishment 

 to the enclosed animal, di'awiug it from the surroimding 

 parts, and throwing it into the cavity, the structure and 

 action being identical with that in the encysted tumours as 

 already described. 



The bulbous extremities of the cysts of Trichina spiralis 

 contain masses of germinating cells, to which I am inclined 

 to attribute the same function. 



Figs. 8, 9, 11. The clavate extremities of the cy.sts of Trichina spiralis, 

 with their germinating absorbent cells. 



The epithelium and absorbent cells of the cysts of the 

 entozoa may be considered as permanent yelk-cells in the 

 economy of these persistent embryos. 



Figs. 1 and 3. Magnified drawings^ of Sarciiia ventriculi described, but 

 badly figured by me in the Edinhurgh Medical and Surgical 

 Journal, No. 151. I am still of opinion, notwithstanding 

 the arguments of ]\Ir. Busk, in the Microscoincal Journal, that 

 this body is a vegetable parasite, its svidden occurrence and 

 sudden disappearance being not more extraordinary than the 

 rapid development of many cellular structures ; the glandular 

 epithelium, for instance, duiing secretion. That it is a 

 Gonium, as has been suspected by Professor Link, ajii^ears to 

 me improbable, as would be admitted, I believe, by that 

 great botanist, if he had had an opportunity of observing its 

 peculiar vegetable aspect, so different from that of an in- 

 fusorial animal. 



