540 ALFRED 0. HADDON. 



bud. I would point out that his pi. xi, figs. 7 — 9, and 12 — 

 15, suggest a double origin of the alimentary organs, and that 

 the connection between the cavity of the lophophore and the 

 lumen of the stomach occurs comparatively late. 



The account of the development of Alcyone 11a by Dr. 

 AUman is unfortunately far from satisfactory, and I would 

 venture to suggest another interpretation (fig. 4) of the stage 

 represented in pi. xi, fig. 30, and by No. 4, fig. 5, p. 34, 

 which is, that the polypide is developed from the remains of 

 the archenteron of the embryo, probably by a direct conversion 

 of the walls and of the lumen of the archenteron into those of 

 the alimentary tract of the young polypide. The lophophore 

 and oesophagus would be derived from the overlying epiblast. 

 The remainder of the body wall of the embryo, consisting of 

 epiblast and peripheral mesoblast, " becomes enveloped in an 

 ectocyst, to constitute the cell of the adult polyzoon. The sub- 

 sequent changes are produced by the gemmation of new poly- 

 pides, with their proper ectocysts and endocysts " (p. 35). In 

 other words the embryo passes over entirely into the first adult 

 of the colony. At a very early stage, between figs. 30 and 31, 

 a second polypide makes its appearance ; there is little doubt 

 that this second bud is constricted off from the older polypide, 

 although Allman leaves one to suppose that it, like the former, 

 " appears to take place in a manner quite similar to that by 

 which new polypides are produced by gemmation from the 

 walls of the endocystal cavity in the adult" (p. 34). It is 

 very unfortunate that Allman should have derived the alimen- 

 tary canal from the epiblast, when hypoblast already was 

 present in the embryo. 



'^Plumatella fruticosa presents similar developmental 

 phenomena ; the ciliated larva, however, in this species, differs 

 from that just described, in having its polypide single." 



I do not propose to discuss the morphology of the statoblasts 

 at present. Allman (1. c. p. 38) describes how they take their 

 origin entirely from the funiculus. Ultimately " a young 

 poly/oan gradually emerges and floats away. . . . At the 

 period of its escape it possesses all the essential organization 



