64 



ACALETIIS IN GENERAL. 



Part I. 



It is evident that these (JoniUines oui^ht to be eHmiiiated from the ehass of Polyps, 

 since their vegetal)le nature is proved. 



There are a few more animals Avhirh have Ijeen referred to the class of Polyps, 

 such as the Lucernaria, the Eleutlieria, and the fresh-water Ilydra,^ about the affini- 

 ties of which I shall have more to say hereafter, when considering in detail the 

 II_>-droids and their alternate generations. I leave them aside for the present, a.s, 

 on account of their small munber of representatives, their position in the natural 

 system can in no way affect the natural limits of the classes of Acalephs and 

 Polyps. I shall also take occasion to i>resent some considerations npon the affinities 

 of the Rugosa," a type entirely unknown at the present day, but the representatives 

 of which are found, in large iunnl)ers, in the oldest stratified rocks forming part of 

 the crust of our globe. So long is it since the Tunicata were removed from among 

 the Zoojihyte.s, that there is hardly a naturalist living Avho may rememljer the time 

 when they were confounded with Poly^)s. I need not, therefore, insist here upon 

 their affinities with the Mollusks. 



S E (J T I N III. 



THE CLAS.SES OF KADIATA. 



We have thus flir considered the various types of animals, chiefly with the 

 view of ascertaining which among them are true Kadiata and which are not; and 

 it a]ipears plainly, even from this rapid sketch, that while the Ctenophorai, the 

 Medusa^ proper, the Siphonophora;', the Hydroids, the Halcyonoids, and the Actinoids, 

 are truly radiated animals, this is not the case with the Bryozoa, which properly 

 belong to the type of Mollusks, nor with the Corallines, which are genuine Plants. 



' IMiliw-Kdwiirds refers the fjemis Hydra to tlie 

 same elass, U> wliieh lie ivters also the Anthiizoa,, 

 the Tabidata, and the Eiigosa, wliich lie ealls Zo- 

 antliaria, separating, however, the genus Hydra, as a 

 distin<'t snh-elass ; Leuekart, on the contrary, jdaces 

 it. among the Hydroids proper. Many important 

 ))aiiers have lately lieon jinblished npon the structure 

 of this type, but with conflicting results. "While 

 this iiagc" was in the printers' hands I received No. 

 31 of the Quarterly Journal of Microscopical Sci- 

 ence for April, 18G0, in which I lind Prof. Allman's 

 descriiition of a new genus of Lncernarioid Hydroids, 



called Carduella, showing, more distinctly perhaps 

 than Lucernaria proper, the Acalephian character 

 of this famil}', on one hand, and also its affinity 

 to the Rugosa, as well as to the embryonic forms of 

 the higher Discophora'. 



- If, as I believe, not only the Talinlata, but 

 .also the Rugosa, belong to the Acalephs, the exist- 

 ence of this class upon our globe, instead of be- 

 ginning in the Jurassic period, dates from the 

 earliest geological ages characterized by the presence 

 of organized beings. Thus far the tddest Acaleph 

 known, was a Medusa from Solenhofeii. 



