188-l.j 135 [Hyatt. 



Nat. Hist., ser.2, vol. n) is an able discussion of the Protozoonal 

 characteristics of the Porifera. His efforts to show that these 

 affinities are sufficient to justify the association of Porifera and 

 Choanoflagellata, are, however, founded upon conceptions of the 

 structure of the former which do not seem to us to be admissible. 

 Mr. Kent has not detected the chorion, and in consequence has 

 supposed Carter, the discoverer of this structure, to have been in 

 error when he asserted that the segmentation of the sponge ovum 

 always takes place inside of such a special envelope. This fact as 

 has been stated above is unquestionable, and one of Mr. Kent's 

 strongest points, that the poriferan ovum is not a true Ggg, falls 

 to the ground. 



Another of Kent's views is that the ampullae are developed 

 from ova-like bodies in the mesoderm, and are mere aggregates 

 of Protozoa; but the series, which he figures as proof, is open to 

 serious criticisms. The author must have confused the early 

 stages of an ovum (pi. 7, f. 1-4) with a fully matured spermatocyst 

 (pi. 7, f. 5), and a no less mature stage of the same body (f. 6), 

 A spermatocyst (f. 5-6) with its included zoons is thus presented 

 as one of the younger stages of the ampullaceous sac (f. 7). The 

 chorion appears in Mr. Kent's figures 2-3 of this series, is not pres- 

 ent in figures 4-6, and is of course absent in his ampulla (f. 9) 

 which forms part of the same series of figures. 1 Thus Mr. Kent 

 mixed up ova, spermatccoysts, and ampullae in his observations, 

 and he was, therefore, unable to distinguish true ova among 

 sponges, and has been led to make an erroneus estimate of the 

 affinities of the Porifera and choanoflagellate Protozoa. Never- 

 theless many of Mr. Kent's comparisons, appear to us to prove a 

 much closer relationship between the Protozoa and Metazoa than 

 has been heretofore admitted by the opponents of this view. 



An undoubted Protozoon, Proterospongia Haekelii (Man. Inf., 

 vol. i, pi. xii, p. 365) is described by the author as " a stock form 

 from which all the sponges were primarily derived." This col- 

 ony of flagellate and collared cells buried in a structureless jelly 

 does not essentially differ from the single layered colonies of the 



Dr. Wilson (Mittheill. aus. d. Zool. Stat. Neapol, vol. 5, pt. 1) observed similar 

 phenomena in the mesenterial filaments of the Alcyonaria. Metschnikoff also has 

 made us familiar with other examples of a similar sort in his interesting article tran- 

 slated in Quart. Journ. Micr. Sci., Jan., 1884. 



1 A part of these same figures is given in the Manual of the Infusoria, pi. 9. 



