NOTICES OF IRISH ENTOZOA. 69 



progress is in a contrary direction, — that in its first stage of 

 being, the head is formed in the peritoneal coat, and that from 

 it the neck penetrates the other tunics, and that afterwards 

 the body is developed. 



In support of this opinion I may at present mention, that 

 besides the tubercles on the outside of the intestine of the 

 tufted duck, to which were appended the bodies of perfect 

 Entozoa, hanging free in the intestinal cavity, there were 

 many other similar tumors having no such appendages, and 

 on examining these I found the head of Ech. Jilicollis, with 

 its enveloping coats, its central umbo, and the stria running 

 from it, similar in all respects to the head of the fully deve- 

 loped animal, but the neck was a pedicle of about two, or at 

 most three, lines in length, terminated by a blunt, conical 

 point, but not entering into any coat of the intestine, the pe- 

 ritoneal excepted, in which it was involved. It may be ob- 

 jected that these were the heads of perfect Entozoa, whose 

 bodies had previously dropped off, and this idea occurred to 

 me in their examination, but I could perceive no circumstance 

 in any way favouring such a supposition. I am ready to ad- 

 mit, however, that much more observation will be required to 

 settle this point as an absolute matter of truth, but in the 

 mean time I am much inclined to suppose that various intes- 

 tinal Entozoa have their embryotic period of existence in the 

 2ieriton<Bum, and are afterwards developed into their final 

 state by prolongation through the other intestinal coats into 

 their common cavity. This I suspect to be the case with the 

 Bothriocephalus so common in the cod, the head of which is 

 always lodged in a curved irregular tumor, on the outside of 

 one of the pyloric appendages, while the body hangs free in 

 the duodenum.* 



The Ech. Jilicollis absorbs water, but by no means so ra- 

 pidly as any others of the same genus which I have examin- 

 ed, and in several of the specimens which I obtained from 

 the tufted duck, the process was defective both at the anterior 

 and posterior ends, while it was nearly perfect in the middle, 

 so that the centre was swelled and the extremities narrow, 

 exactly as the Ech. spharocephalus is described by Rudolphi, 



1 On enquiring from Dr. Bellingham whether he had ever detected the 

 head of this species, he thus writes, — " I have seldom examined a cod that 

 I have not found the Bothriocephalus you mention ; that it is a Bothrioce- 

 phalus appears, I think, from the situation of the ovaries. I have never 

 been able to unravel the head, so as to examine it, although I have drawn 

 it out to a fine point, but could see neither depression nor oscula." Dr. B. 

 farther states that he is sure it is a new species, and suggests for it the very 

 appropriate specific title of cryptocephalus. 



