470 R. M. PACE. 



(2) Segmeutation aud cell-lineage liave been followed out 

 in detail up to tlie 32-cell stage. 



(3) The formation of the endoderm has been traced. 



(4) The oral and aboral ectoderm are differentiated as 

 early as the 16-cell stage, and remain quite distinct from that 

 time onwards. 



(5) The ciliated ring of the larva is formed by the coales- 

 cence of several originally distinct rows of cells, and not by 

 the hypertrophy of a single row. 



(6) A stomach, comparable to that of Alcyonidium, is 

 present also in Flu st re 11a. 



References. 



1. Bambeke, C.v. — "Contributions a I'liistoire de la conslitutiou de I'oeiif," 



iii, "Reclierclies sur I'oocyte de Pliolcus plialangioides (Fuesbl.)," 

 • Arch. Biol.,' vol. xv, pp. 511-598, pis. xxiii-xxviii, 1898. 



2. Bakhois, J. — ' Recherclies sur I'Embryologie des Bryozoaires,' Lille, 1877. 



3. Bahrois, J. — " Menioires sur les metamorphoses des Bryozoaires," i, 



"Metamorphose des Escharines," 'Ann. Sci. Nat.,' ser. 0, Zool., 

 vol. ix. No. 7, 67 pp., pis. xiii-xvi, 1880. 



4. Bkaem, Fkitz. — "Untersuchungen iiber dieBryozoendes siissen Wassers,'' 



' Bibliotheca Zoologica,' No. vi, Cassel, 1890. 



5. BiiAEM, Fritz. — "Die geschlechtliche Entwickelung von Paludicella 



Ehrenbergii," 'Zool. Anz.,' vol. xix, pp. 54r-57, February, 1890. 



6. Braem, Fritz. — "Die geschlechtliche Entwickelung von PI u mat ell a 



fungosa," ' Zoologica," Heft 23, Stuttgart, 1897. 



7. Calkins, G. N. — " Observations on the Yolk-nuclcus in the Eggs of 



Lumbricus," 'Trans. New York Acad.,' vol. xiv, pp. 222-230, 1895. 



8. Calvet, L. — " Contributions a I'liistoire Naturelle des Bryozoaires 



Ectoproctes Marins," 'Trav. Inst. Zool. Montpellier,' ser. 2, No. 8, 

 1900. 



9. Crampton, 11. E. — " Studies upon the Early History of tiie Asciiiian 



Egg." Part I. — "The Ovarian History of the Egg of Molgula 

 manhattensis," ' Journ. Morphol.,' vol. xv, suppl., pp. 29-5G, pi. iii, 

 December, 1899. 



10. Foot, K.— " Yolk-nuclcus and Polar Rings," 'Journ. Morjthol.,' vol. xii, 



pp. 1-lG, pi. i. May, 189G. 



11. Harmeb, S. F. — " Sur I'enibryogcnie des Bryozoaires ectoproclcs," 



' Arch. Zool. Expt.,' ser. 2, vol. v, pp. 443-458, i)ls. xxvii, xxviii, 1S87. 



