ZOOPHYTES. 347 



No trace of cilia, nor any appearance of ciliary motion, 

 was perceptible during life. 



When I first discovered these strange beings, I was as 

 much astonished by what I saw as you are ; nor could I 

 imagine to what class of animals they were to be referred. 

 Neither did I know whether their presence on the tube 

 of the worm was a mere accident, or whether it indicated 

 a predominant instinct. On both these points, however, 

 light has been shed. 



This larger Sabella tube was not the only one infested 

 with the parasites. I observed them on at least two 

 smaller specimens of the same species, in the same situa- 

 tion, and with precisely the same movements. The ex- 

 tremity of one of those smaller tubes I cut wholly off, and 

 placed in the live-box of the microscope. Two of the 

 parasites only were on it, which were active at first, but 

 in about an hour — probably from the exhaustion of the 

 oxygen in the small quantity of water inclosed — they de- 

 composed, or rather disintegrated, the outline dissolving, 

 and the external cells becoming loose and ragged, and the 

 whole animal losing its definite form. 



One of these specimens, however, while yet alive and 

 active, afforded me an observation of value. I had al- 

 ready associated the form conjecturally with the Hydroid 

 Polypes, and was inclined to place it in the family Cory- 

 nidce, considering the arms to be tentacles, and the head- 

 lobe to be homologous with them in character, but ab- 

 normal in form. It appeared to be a three-tentacled 

 Coryne, with the tentacles simple instead of having heads. 

 But while I was observing the individual in question, I 

 saw it suddenly open the head-lobe, and unfold it into the 

 form of a broad shovel-shaped expanded disk, not, how- 

 ever, flat, but with the two halves inclining towards 

 each other, like two leaves of a half-opened book. This 

 immediately reminded me of the great sucking-disk 

 which, as I lately told you, I had seen evolved from the 



