68 THE MICHOSCOPE. May 



or by other causes. They are not rhythmical ; each in- 

 dividual appears to be animated by a distinct volition. 



Applying a higher magnifying power than we have yet 

 use to these animals, we find that the head-lobe encloses 

 a central cavity ; that the arms are also hollow, with 

 thicli walls, marked with transverse lines, indicating 

 flattened cells, and muricated on the exterior ; and that 

 the body contains an undefined, sub-opaque nucleus, 

 doubtless a stomachal cavity. 



I cut out, with fine scissors, a segment of the tube, in- 

 cluding two of the parasites, with the portion of the net- 

 work of threads that carried them. They have become 

 immediately paralysed by the division of the threads, 

 but those that remain on the tube are unaffected by the 

 violence. Subjectiug one of the animals so cut out to the 

 action of the compressorium, with a power of 560 di- 

 ameters, the arms are seen to be formed of globose cells, 

 made slightly polyhedral by mutual pressure, set in 

 single series. 



The interior of these organs is divided by partitions, 

 placed at intervals of about the diameter. Some at least 

 of the cells contain a bright excentric nucleus. 



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 cilliary 

 motion was perceptible during life. 



When I first discovered the strange beings, I was 

 much astonished by what I saw ; 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 pre- 

 dominal instinct. On both these points, however, light 

 has been thrown. 



This larger Sabella tube was not the only one infested 

 with the parasites. 1 observed them on at least two 



