106 BULLETIN OF THE 



4, 5, of Figure A. The buds* which give rise to new compartments may 

 be called lateral buds, iu accordance with Braem's terminology; those 

 which prolong the ancestral branch, median buds. Where only one 

 individual arises, it is a median bud. These conclusions regarding the 

 relationship of buds are based solely upon the length of the radial par- 

 titions, the inner extremities of which correspond to the angle formed 

 by two branches iu branching genera like Plumatella. 



Thirdly, while the lateral buds. Figure A, 4, 5, and 12, 13, give rise 

 directly to new buds, median buds of the same or younger age, 6, 14, have 

 moved to a considerable distance from their mother buds before giving 

 rise to new individuals. The eflfect of this is, that the median bud 

 comes to lie, not alongside of the lateral bud, but in a quincunx position 

 relatively to it. 



Fourthly, lateral buds (branches) may arise from either side of the 

 budding individual. Although most of the branching in the part of 

 the colony figured in the out is to the right, yet the youngest lateral 

 buds are being given off to the left. So in compartments 4, G, 7, 12, 

 the funiculus indicating the point where the median bud will arise. 



To recapitulate : The descendants of common ancestors are arranged 

 similarly in the same region of the colony ; a lateral and a median bud 

 may arise from a single individual, the first forming a new branch, the 

 latter continuing the ancestral one ; median buds migrate towards the 

 margin before producing new buds ; and new branches are formed on 

 either side of the ancestral branches. 



III. Origin of the Individual. 



Two essentially different views of the origin of the polypide in the 

 adult colony of Phylactolaemata have been maintained within recent 

 years. The first is that advanced by Nitsche (75, pp. 349, 352, 353), 

 and adopted by Reinhard * ('80*, p. 211, '80^ p. 235). According to 

 these aiithors, the outer of the two layers of the colony-wall gives rise, 

 either by a typical or a potential invagination, to the inner cell layer of 

 the bud, — the layer from which the lining of the alimentary tract and 

 the nervous system both arise, — and pushes before it the inner layer 



^ Reinhard says in his preliminary article, " Meiner Meinung nach entwickelt 

 eich die Knospe in Folge einer Verdickung des Ectoderms, in welclie dann die 

 Zellen des Entoderms eindringen," but Brandt's abstract of the paper read by Rein- 

 hard before the Zoological Section of the Russian Association, places entoderm 

 for ectoderm, and vice versa, — a rendering more in accordance with Reinhard's 

 statements in the context. 



