liv INTUODUCTION. 



this body — that which regards it as the mere lifeless debris 

 of the defunct polypide^ and that which recognizes in it a 

 special structure, derived indeed, from the substance of 

 the histolyzed polypide, but endowed with a reproductive 

 function, and capable of originating a successor to it in 

 the occupancy of the cell. 



The latter opinion has been maintained by the able 

 Scandinavian zoologist, Prof. F. A. Smitt, whose researches 

 have added so largely to our knowledge of the Polyzoa ; 

 and he has supported it by a cousiderdble body of careful 

 observation. My own studies had led me to adopt his 

 view; and on various occasions I have recorded the grounds 

 on which my conclusions were based. The opposite 

 opinion has had able exponents in Nitsehe and Joliet. 

 They find in the " brown body " nothing but the remains 

 of the decayed polypide, a mass of inert material wait- 

 ing to be ejected from the cell. Another interpretation 

 has been adopted by Repiachoff *. To him the " brown 

 body'' is not concerned directly in the production of a 

 new polypide, but at a certain stage it is enveloped by 

 the forming bud in its substance, and serves as pabulum 

 for it during its further development. 



It is quite impossible for me to reproduce in detail the 

 observations which have been adduced in support of the 

 conflicting views. I must refer the student to the works 

 in which they are recorded. The theory of Smitt has 

 been subjected to an elaborate examination by JoHet, in 

 the course of which he has criticised at length and with 

 much acumen my own contributions to the discussion. My 

 object will be to point out how far and in what way the 



* "Ziir Naturgescbichte der chilostomen Bryozoen," Zeitsch. f. wissensch 

 Zool. vol. xsvi. (187fi). 



