Xl INTRODUCTION. 



system of nerves apart from the zooecia, by which the 

 members of the colony are to some extent controlled and 

 brought into relation. He approached it on the physio- 

 logical side, and perhaps, as Joliet has suggested, too 

 much under the influence of an a priori conception. The 

 colonial nervous system, as developed in each branch, 

 consists, according to Miiller (whose observations were 

 made on a Ctenostomatous form) , of ganglia placed at the 

 origin of the branch, at the internodes, and at the base 

 of the zocecia, of a nerve trunk running the entire length 

 of the branch, and of a plexus of nerves resting on the 

 trunk and connecting the ganglia. He also describes a 

 nerve passing from the zooecial ganglion to the polypide. 

 If we compare this scheme with the funicular system just 

 described, we shall at once recognize the general corre- 

 spondence between them. The ganglia are the granular 

 enlargements, at the base of the zooecia and at the inter- 

 nodes ; the trunk is the connective cord ; the plexus is 

 represented by the filamentary processes given off from 

 the latter ; the nerve between the polypide and its gan- 

 glion is the funiculus. The simple question is, will these 

 parts bear the construction which has been put upon 

 them ? 



Miiller's views were adopted by Smitt* (who traced 

 the supposed nervous system in the Cheilostomata] , 

 by Claparedef, and others; indeed for some time they 

 seemed to command very general assent. It is only as 

 the result of minuter histological research, and a more 

 careful study of the general history of the tissue in 

 question, that a change of opinion has set in. I fully 



* ' Om Hafabryozoornas Utveckling och Fettkroppar,' 1805, p. 31-33. 

 t "Beitrage z. Anat. und Entwicklungsgesch.^Ton Secbryozoen," Zeitsch. 

 f. wifench. Zool. ixi. 



