ZOOPHYTES. 347 



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 these 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 already 

 associated the form conjecturally with the Hydroid Polypes, 

 and was inclined to place it in the family Corynida, con- 

 sidering the arms to be tentacles, and the head-lobe to be 

 homologous with them in character, but abnormal in form. 

 It appeared to be a three-tentacled Coryne, with the ten- 

 tacles 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 however 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 obtuse summit of Stauridia producta, 



