398 EVENINGS AT THE MICEOSCOPE. 



including two of the parasites, with the portion of the 

 network of threads that carried them. They have be- 

 come immediately paralysed by the division of the 

 threads, but those that remain on the tube are unaffect- 

 ed by the violence. Subjecting one of the animals so 

 cut out to the action of the compressorium, with a 

 power of 660 diameters, 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 small bright excentric nucleus. 



When the tissues were quite crushed down by the 

 pressure of the compressorium, a quivering motion was 

 visible among the disjointed gi'anules, but it was very 

 slight. 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. ]!^either did I know whether their presence 

 on the tube of the worm was a mere accident, or 

 whether it indicated a predominal instinct. On both 

 these points, however, light has been shed. 



This larger Sabella tube was not the only one in- 

 fested with the parasites. I observed them on at least 

 two smaller specimens of the same species, 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 exhaus- 

 tion of the oxygen in the small quantity of water in- 



