66 BULLETIN OF THE 



which forms the gastric coecum, grow round and envelop the brown body, 

 so that the brown body passes as a whole into the alimentary tract of the 

 young Flustra." It seems to me that the burden of proof of such a 

 remarkable occurrence lies with him who asserts its existence, and cer- 

 tainly sufl&cient evidence is not presented by Haddon. 



To settle this question in my own mind, I cut a series of thin sections 

 through a part of a stock of Escharella (which in budding shows a prac- 

 tical identity with Flustra), in which all stages of regenerating polyp- 

 ides were to be found. From complete series, at critical ages, I utterly 

 failed to find any indication of the inclusion in toto of the brown mass 

 by the polypide. But I found the alimentary tract of the polypides 

 usually applied to the brown body (p]/d. dgn.), as shown in Figure 92. 

 At this stage the degenerated mass is surrounded by spindle-shaped cells, 

 and just within these by a homogeneous or lamellated sheath. At later 

 stages the elements of the degenerated mass were seen to be more loosely 

 associated. The cells of the alimentary tract at the same time appear 

 highly granular, and a granular coagulum often partly fills the alimentary 

 tract. Before the new polypide is ready to expand itself, the brown body 

 as such has often wholly disappeared. Just as my sections leave no 

 chance for the brown body to be included en masse by the alimentary 

 tract, so too do they yield no evidence of the addition to the latter of 

 new cells from this degenerate mass, as Ostroumoff, in the sentence 

 quoted above, implies. 



The interesting facts of degeneration in Bryozoa deserve a more careful 

 study than I have been able to give them. We are quite ignorant of the 

 physiological significance of the regularly recurring degeneration and 

 regeneration in certain Bryozoan colonies. OstroumoflF ('86% p. 339) has 

 offered an interesting hypothesis, to the effect that the degeneration of 

 the polypides, the remains of which are taken into the stomach of the 

 regenerated polypide and the undigested portion of which is cast out with 

 the fseces, is a method of excretion, made necessary to these animals from 

 lack of urinary tubules. 



IV. Origin of the Gemmiparous Tissue in Phylactolaemata. 



After having found that in Paludicella and the marine Bryozoa, as in 

 Phylactolaemata, the growth of the colony takes place at the margin or 

 tips, and that it is here primarily that buds originate, and after having 

 thus found that throughout the group all of the oi'gans of the polypide 

 are derived from two layers, of which the inner gives rise to organs so 



