44 BRYOZOA ECTOPROCTA. 



of the brown body. A certain difficulty attends this assumption, in consequence 

 of the development of the intestine in the young bails, in ■which there is no 

 brown body. Ostkoumoff, however, tries to escape these difficulties by 

 pointing out the relations established by the funicular tissue between the 

 parent-zooecium and the bud, as well as by assuming that in this way ento- 

 dermal cell-masses pass from the parent into the bud. In this respect the 

 views of Ostkoumoff have something in common with those of H.\1)D0N, 

 who held that all the three germ-layers of the parent-zooecium took part in 

 the formation of the bud. According to Joliet (No. 17), the alimentary canal 

 of the developing polypide does not originate from the inner layer of tlic 

 bilaminar sac-like polj'pide-rudiment, but from a distinct cell-mass derived from 

 the outer layer of that rudiment. The inner layer of the polypide-rudiment 

 would then yield only the ectodermal parts of the polyjjide, while the outer layer 

 would contain the mesodermal and entodermal parts. In any case, according 

 to Joliet, the enteric canal (mid-gut) has an origin distinct from that of the 

 ectodermal rudiment. The most recent researches, how^ever, confirm the view 

 that the whole intestine of the polypide originates from the inner layer of the 

 double-walled sac, i.e., from the ectoderm, but Prouho differs to some extent 

 from the de.scription given above and founded on the statements of more recent 

 authors, for he regards a small mass of irregularly-arranged cells, lying at the 

 end of the diverticulum d in Fig. 20, as the rudiment of the mid-gut, while the 

 hind-gut arises exclusively from the diverticulum itself. According to Prouho, 

 indeed, this cell-mass is to be derived from this same diverticulum ; but it 

 cannot be denied that this statement is likely to strengthen the doubt that lia.s 

 long been felt as to the common origin of the fore-, mid-, and hind-guts. 



V. Asexual Keproduction of the Ectoprocta. 

 A. Budding. 



In the Biyozoa, the colonies are produced by the continuous 



budding of the primary individual. The nature of this budding 



has been carefully studied by Nitsche (Nos. 23 and 52), and more 



recently by Braem (Xo. 45a) and Davenport (Nos. 11 and 46a).''' 



Two kinds of buds may usually be distinguislied, according to 



the direction of their growth: — (1) those that continue to grow in 



the same direction as tlie parent-zooecium, sucli buds serving for the 



direct prolongation of the branch or branchlet to which the parent- 



zooid belongs ; and (2) those that, in growing out from the 



parent-zooecium, take a new direction and thus give rise to new 



branches. In many cases the new branches grow out laterally. 



The buds of the second kind are then lateral huds, while the median 



buds provide for the continuation of the branches, such individuals 



usually continuing in the same axial direction as the parent. It 



should, however, be mentioned, that in many cases median buds 



may also give rise to new branches, since, while retaining the same 



plane as the mother, they may take a new direction. 



* [For the develojimcnt of the colony in the Gymiiolaemata, see important 

 papers by Hakmeu on Lichcnojwra, Crisia, and Tuhidipora. Quart. Journ. 

 Micro, ,'i'ci., Vols, xxix., xxxii., and xli. — Ed.] 



