400 POLYZOA HYPPOCREPIA. 



polypes (the accuracy of which was vouched for by Lamouroux !) 

 differed in so many obvious particulars from Trembley's, that no one 

 could suspect their identity, the more especially as the figures of the 

 polypidoms were equally dissimilar. Bosc's polypidom was therefore 

 catalogued in our systems as an Alcyonella, and Trembley's as a spe- 

 cies of Plumatella. Thus matters stood when Raspail was led, in 

 1826 and 1827, to examine the subject, and the result of his inge- 

 nious labours has been very curious, though some of his conclusions, 

 notwithstanding the boldness of their enunciation, seem to me un- 

 proved, and one of them, which identifies the Cristatella with the 

 Alcyonella, has already been shewn to be erroneous. He has, how- 

 ever, demonstrated very satisfactorily the entire sameness of the Po- 

 lypes a Panaches of Trembley, the Bell-Flower Animal of Baker, and 

 the Alcyonella of Lamarck, the variations in the polypidom, which 

 had deceived all others, being produced by age, or by external and 

 fortuitous circumstances, as, for example, by peculiarities in its site : 

 when this is the floating leaves of Letnna?, or the upper or under 

 side of a stone, the development is diffused, or lobed, or arborescent, 

 or creeping, or massive and spongy, according as the polypidom has 

 freedom to spread, or is restrained by its position, or is influenced by 

 the mere gravitation of one part against another. I can find, how- 

 ever, in the beautiful series of figures which illustrate his Memoir, 

 none to make me assent to Raspail's opinion that all the Plumatellsa 

 are certainly mere variations of this zoophyte : at present the facts 

 appear rather of an opposite tendency ; while, on the contrary, sub- 

 sequent observations have shewn that he is right in considering as 

 embryo Alcyonellae the Leucophra heteroclita and Trichoda floccus of 

 Miiller, as well perhaps as the Difflugia proteeiformis of Leclerc, 

 although Ehrenberg declares against this conclusion. 



Raspail's description of the zoophyte is admirable, and is rendered 

 peculiarly interesting from the generalizations in physiology which 

 the author ever and anon boldly hazards on certainly a very narrow 

 basis ; and the curious experiments detailed in it. He has fully re- 

 cognized the merits of Trembley, and has confirmed his accuracy in 

 most particulars ; he has explained the cause which led Trembley 

 erroneously to ascribe a retractor muscle to the body, the appearance 

 being the result of a fold or plait in the tunic in certain positions of 

 the body : he ascertained the position of the anus ; gave a complete 

 view of the tentacular apparatus, and an inimitable anatomy of the 

 ova, which we shall transcribe at least in part. The ova, he says, 

 are in general one-third of a millimetre in their longest diameter. 



