MOVEMENTS OF VIBRACULA IN CABEREA BORYI. 



Note on the Movements of the Vibracula in Caberea 

 BoRYi, and on the supposed Common Nervous System in 

 the PoLYzoA. By the Rev. Thomas Hincks, B.A., 

 F.R.S. 



The theory of a common or colonial nervous system in 

 the Polyzoa, first propounded by Fritz Miiller, must be re- 

 garded as still subjudice. The question may be approached on 

 two sides, the histological and the physiological. Miiller's 

 attention seems to have been first drawn to the subject by 

 the behaviour of the polypides in certain cases which, ap- 

 peared to point to the existence of a system of nerves apart 

 from the individual cells, by which the members of the 

 colony are to some extent controlled, and brought into rela- 

 tion. He refers specially to the energetic movements of 

 the peduncle of Pedicellina, after the fall of the body, and 

 to the simultaneous movements of the cells in Mimosella 

 gracilis, a fact which I had previously observed and recorded. 

 He was thus led to investigate the stems and branches of 

 some of the Ctenostomata, and demonstrated the existence 

 of the (supposed) ganglia and trunks of the colonial system. 

 Smitt adopted his views and made similar observations on 

 the Cheilostomata. 



Their conclusions have been criticised by E-eichert and 

 Nitsche, and more recently by Joliet. These writers are 

 agreed in regarding F. Miiller's doctrine as erroneous. View- 

 ing the subject anatomically and histologically they arrive 

 at the same result, that the structure which Miiller and others 

 have described as a colonial nervous system, has in reality 

 has a very different significance. Reichert regards the cords 

 and network of threads that occur in the stems of the 

 Ctenostomata as a medium of communication between the 

 polypides of a colony, and as a channel by which stimuli 

 applied to the coenoecium may be transmitted and diffused, 

 but denies that they have the character of a true nerve- 

 tissue, Nitsche takes much the same ground with reference 

 to the Cheilostomata. Joliet, as the result of histological 

 investigation chiefly, gives a decided verdict against F. 

 Miiller's interpretation. He also states that he has cut in 

 two the supposed nerve-trunk pervading a branch, and that 

 the polypides expanded on the same branch did not retract 

 themselves, a fact which seems to tell with as much force 

 against Reichert's view as against Miiller's. He identifies 

 the supposed nerve-threads passing to the body of the 

 polypide from the stem with the funiculus. 



