MUSEUM OF COMPARATIVE ZOOLOGY. 121 



1. Origin of the Polypide. — Lateral budding (as distinguished from 

 linear budding, such as occurs in Turbellaria, Chsetopods, &c.) may 

 be roughly classified under two types, in one of which the young indi- 

 vidual arises directly from the body-wall of the parent, as in Hydra. 

 In the other, the young arise, one after the other, from a mass of 

 embryonic material derived from a parent individual, — from a stolon, 

 as in Salpa. In the group of Bryozoa both of these methods seem to 

 be present. In such a form as Paludicella (Allman, '56, pp. 35, 36, 

 Korotneff, '75, p. 369) we have an example of the direct type; in Pedi- 

 cellina we have a stoloniferous genus. Also in the marine Ectoprocta 

 examples of both types appear to occur (e. g. Flustra, Hypophorella). 

 To which of these classes does budding in Cristatella belong] It seems 

 to me that we have here an instructive example of a transitional condi- 

 tion. The young polypide of Figure 3 arises directly from the mother 

 polypide, and may represent a case of the first class. Is the type of 

 Figure 2 a representative of the stoloniferous class? It seems to me 

 that it partakes of the essentials of that class, although, as I have 

 shown, it may be united by intermediate stages with the first class. 

 I understand a stolon, in its morphological sense, to signify a mass of 

 embryonic cells derived from a parent individual, and capable of repro- 

 ducing non-sexually one or more daughter individuals at some distance 

 from that parent. The condition shown in Figure 15, Plate II., in which 

 the embryonic cells of the two layers represent the stolon, may fairly 

 be said to answer to this definition. The mass of cells (III.) represents, 

 then, the distal end of the stolon. But the stolon does not end here, 

 although its further progress towards the margin is delayed. Not all 

 of its cells go to form the polypide which arises at this place. On the 

 contrary, some of them remain in the "neck" of the new polypide, in 

 an indifferent histological condition, and later give rise, either directly, 

 or by the intervention of a typical stolon, or by both, to one or two 

 new buds. Those cells of the neck which do not thus pass over into 

 new buds for the most part degenerate (page 144). According to this 

 view, the neck of the polypide is to be regarded as at first essentially 

 a portion of the stolon. 



2. Interrelation of the Individuals in the Colony. — The interrelation 

 of individuals in the colony in Cheilostomata has been most carefully 

 investigated from a morphological standpoint by Nitsche ('71, pages 35, 

 36), who showed that, in opposition to Smitt's theory, each new indi- 

 vidual arose from a single preceding one, and that the latter, in order 

 to increase the breadth of the colony, might give rise to two individuals 



