114 MR. GOSSE ON A NEW FORM OF CORYNOID POLYPES. 



and remained nearly in contact with the Annelid's body, moving but slightly ; but no 

 sooner did it retire, than they began instantly to bow forward, and gestictQate as before. 

 These movements were continued, so far as I observed, all the time that the Sabella was 

 retracted ; and were not in any degree dependent on currents in the surrounding water, 

 whether produced by the action of the Annelid, or by other causes. They were not 

 rhythmical ; each individual appeared to be animated liy a distinct volition. 



Applying a higher magnifying power than I had yet used, to the animals, I found that 

 the head-lobe enclosed a central cavity ; that the arms were also hollow, with thick walls, 

 marked with ti'ans verse lines (internal septa?), and muricated on the exterior; and that 

 the body contained an undefined sub-opake nucleus (see fig. b), doubtless a stomachal 

 cavity. 



I cut out with fine scissors a segment of the tube, including two of the parasites, with 

 that portion of the network of threads that carried them. They were immediately 

 paralysed by the division of the threads ; but those that remained on the tube were 

 imaffected by the violence. The hiatus in the continuity of the circle was healed in a 

 day or two ; not by the approach of the divided edges of the tube, but by the shootiag of 

 the threads across the chasm. One of the animals thus cut out is represented (at d), as 

 it appeared immediately after the excision, magnified 240 diameters. When subjected to 

 the action of the compressorium, with a power of 560 diameters, the arms were seen to be 

 formed of globose cells, made slightly polyhedral by mutual pressure, set in single series 

 (fig. e). The interior of these organs was divided by septa, placed at intervals of about 

 the diameter. Some, at least, of the cells contained a small bright excentric nucleus 



(fig-/)- 

 When the tissues were quite crushed down by the pressure of the compressorium, a 



quivering motion was visible among the disjointed granules ; but it was very slight. No 



trace of cilia, nor any appearance of ciliary motion, was perceptil^le during life. 



This larger Sabella-t\i\^e was not the only one infested with the parasites. I observed 

 them on two, at least, of the smaller specimens, in the same situation, and with precisely 

 the same movements. The extremity 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 enclosed— they decomposed, 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, f^fforded me an observation 

 of value. I had already associated the form with the Hydroid Polypes, and was inclined 

 to place it in the family Corynidce, considering the arms to be tentacles, and the head- 

 lobe to be homologous mth them in character, but abnormal iu form. It appeared to be 

 a three-tentacled Coryne, with the tentacles simple instead of capitate. 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 (fig. g). 

 This immediately reminded me of the great sucking-disk, which I had seen evolved from 



