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portion, dilating into what has been described above as the adnate portion of the peristome, 

 which gives off other "stolons". 



Some of the 'Siboga' specimens show embryos, in the situation which has been indicated 

 bv previous authors, and in particular by Prouho j ). The embryos develop, according to this 

 author, in the body-cavity, at the distal end of a zooecium, three or four being present at one 

 time. When the larva has reached its full development, it pushes out the body-wall of the 

 zooecium and thus gives rise to a hernia-like protrusion, into which it passes. The outgrowth 

 eventually bursts, the larva escaping directly to the exterior. Small tubes projecting from the body- 

 wall may remain as indications of the spots where larvae have escaped in this way. Prouho's 

 account appears to be based on the actual observation of the escape of the living larvae. 



Specimens which agree closely with Prouho's description are figured in this Report 

 (PI. IV, figs 10 — 12, 17). In fig. 10 an additional length of peristome has been added by 

 regeneration. At the distal end of the older part an egg is visible; while at the distal end of 

 the regenerated part there are two embryos. In fig. 1 2 three embryos occur in a similar position, 

 In fig. 17 two embryos are seen, near the middle of the length of the zooecium, each enclosed 

 in a thin hernia-like protrusion of the body-wall. It may be assumed, in view of the evidence 

 brought forward by Prouho, that these would shortly have escaped to the exterior. In fig. 1 1 

 there is again evidence of regeneration of the distal end of the zooecium. The younger part 

 contains an embryo distally ; while more proximally it shows irregularities in its outline, indicating 

 that embryos have escaped in this region. An egg is present in this part, so that the process 

 would probably have been repeated here. 



Figs 19 and 20 possibly represent a different species. The vestibule contains several 

 rounded bodies which may be eggs. I cannot obtain certain evidence on this point; but if the 

 bodies in question are really of this nature, the specimen (108. P.) probably belongs to a distinct 

 species, characterised by producing eggs which pass into the vestibule, either undergoing their 

 development there or reaching the exterior and developing in the water outside, as in certain 

 other Polyzoa {JMembranipora pilosa, Alcyonidium albidum, HypopJiorclla expansa) which have 

 been described by Prouho 3 ). To this list of species, in which the egg is laid and undergoes its 

 development in the external water, may be added Pahidicella articu/ata (Braem, alluded to 

 above, p. 44) ; while Calvet 3 ) states that this is the case in Alcyonidium cellarioidcs, Pherusa 

 tubulosa and Flustrella hispida. It may, however, be remarked that the inclusion of Pherusa in 

 this list is directly opposed to the account which has been given by Prouho *), who states that 

 the embryos develop in the tentacle-sheath of an atrophied polypide ; and that the development 

 of the embryo of Flustrella hispida takes place inside the zooecium, as I have myself observed; 

 while Mrs Pace 5 ) has published an account of this species which shows that the position in 

 which the embryos develop is identical with that described by Prouho for Pherusa. 



1 PROUHO, II., 1892, u Contr. Hist. Bry.", Avch. Zool. Exp. (2) X, p. 626, PI. XXIV, figs 14 — 17. 



2) Ibid., t. cit , p. 607, and elsewhere. 



3) Cai.vet, L., 1900, "Contr. Hist. Nat. Bry. Eet. Mar.", Trav. Inst. Zool. Univ. Montpellier, N. S., Mem. 8, p. 260. 



4) Prouho, H., t. cit., p. 565. 



5) Pace, R. M., 1906. "Early stages Dev. Flustrella hispidd\ Quart. J. Mier. Sci., I., p. 451. 



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