Biblioyrophical Xuiices. .'J 17 



direct contact with the circumfluent water ; and wlien this i.< at rest, 

 all Tiibiilarue sj)rcad wide their tentacuhir circle. But they are not 

 the sole orj^ans of this function, for ue may safely suppose that the 

 water, in jjcnetrating into the common cavity of the poh'pidom, car- 

 ries with it the necessary oxygen. In these animals in fact the func- 

 tions of respiration and nutrition are so simple, and so intimately 

 blended with the circulation, that we can scarcely use separate terms 

 in defining them. 



The stomach of every individual pol)'^p communicates witli the 

 cavity common to all the polyps of the same polypidom, the line of 

 separation being marked only by a sort of stricture ; but in Cvri/tie 

 this is not the case, for the stomach of every individual is isolated 

 and distinct. 



The circulation of the granulous fluid in the common tube of the 

 polyps, first described by Mr. Lister, Van Bcneden is inclined to 

 ascribe to the action of vibratile cilia, which, he admits, he could not 

 detect. The irregularity or inconstancy of this circulation seems to 

 us to be opposed to this explanation ; nor do we perceive any fitting 

 basis on wliich the cilia can be placed. A portion of the tube of a 

 Eudendriinn, some lines in length, being cut away, and consequently 

 open at both ends, preserved its circulating power, the liquid moving 

 in its normiU course. Lister says that the current does not penetrate 

 into the body or stomach of the polyp, but Van Beneden has jjlainly 

 seen it do so. In Coryne and Hydractinia there is no circulation, 

 because of the isolation of the stomach in these genera. 



The second chapter, and principal part of the paper, describes the 

 " erabryogeny." The origin and develo})ment of the reproductive 

 buds and eggs are traced with great minuteness, and illustrated with 

 a series of admirably explanatory figures. There is no distinction of 

 sex in the Tubularia: ; and nothing analogous to spermatozoa, not- 

 withstanding what has been said to the contrary. The reproductive 

 buds, which originate from the bases of the tentacula, are hollow in 

 the centre in all the genera, and always communicate with the di- 

 gestive cavity. What have been mistaken for females are young in- 

 dividuals, which often contain eggs at an early stage even of their 

 development. 



The Tubularia are reproduced (1.) by a bud continuous with the 

 animal whence it pullulates ; (2.) by a free or locomotive bud ; (3.) 

 by a simple eg<^ ; (4.) by a compound c^g or vitellus ; and (5.) by a 

 free bud and eggs simultaneously. Every species may be reproduced 

 by more than one or two of these modes, but it does not appear that 

 any has been observed to reproduce itself by all of them. 



The first or geramiparous reproduction is the simplest. By it the 

 embryo, after having become fixed in a proper site, evolves new in- 

 di\'iduals, and founds a colony where all are associated together. 



2. The free bud originates near the tentacula. It appears at first as 

 a simple tubercle which soon divides successively into several tubu- 

 lar branchlets, in which a circulation goes on as in the main stems. 

 Within the swollen apex of each branchlet a distinct cell soon apjiears, 

 indicating the commencement of the formation of a new being. This 



2 B 2 



