300 FKITZ MULLERj ON THE 



form, the morphological differences among the fully formed 

 parasitic Copepoda will appear to be similarly connected with 

 those with which we have become acquainted in the separate 

 stages of development of the free Copepoda. In the same 

 way that the latter, by a continual multiplication of the seg- 

 mental appendages and segments of the body up to the highest 

 subdivision of the abdomen, proceed one from another, in like 

 manner we perceive in the former almost similar degradations, 

 until at last the organization of the earliest larval form is, as 

 it were, presented as the result of the continued retrogi'es- 

 sion, which ultimately reaches even to the complete loss of 

 the Arthropod character. 



On the Common Nervous Systeji (Kolonialnervensys- 

 tem) of the Bryozoa (Polyzoa), exemplified in Seria- 

 LARiA CouTiNHii, n, sp. By Fritz Muller. 



(From Wiegmann's ' Archiv.' 1860, p. 311.) 



In animals living associated in a common colony or stock, 

 movements of the entire growth or of indi^ddual animals may 

 often be observed — movements which, though spontaneous, 

 do not appear to depend upon the will of the indi^ddual, but 

 to be carried out by them in obedience, as it were, to a com- 

 mand from a higher quarter. This is the case with the Poly- 

 zoa. In a species of PeclicelUna, in which the cell is supported 

 upon a rigid peduncle, 34- mm. long, affixed by a thicker 

 moveable socket, the motion of the peduncle continues un- 

 changed for a whole day after the removal of the animal itself. 

 In a far smaller species of the same genus, which frequently 

 occurs as a parasite upon other Polyzoa and Hydroida, the 

 peduncles, which are moveable throughout their entire length, 

 begin to move in the most active manner at a time when the 

 animal at the summit is scarcely distinguishable in the form 

 of a bud. I also remember noticing in Mimosella gracilis, 

 Hincks, common and simultaneous movements of the disti- 

 chously arranged cells. Now, since in these animals, as in other 

 Polyzoa, the existence of nerves has been demonstrated, it 

 maj' reasonably be supposed that a nervous system exists not 

 only in each Polypide, as the agent of its individual sponta- 

 neity, but that a similar system also exists for the performance 

 of the common or associated movements of the polyzoary 



