Chap. II. SUCCESSION OF ACALEPHS. 125 



SECTION VIII. 



SUCCESSION OF ACALEPHS. 



Thirty-three years ago, Avhile examining the Museum of the Grand Duke of 

 Baden, in Carlsruhe, my attention was attracted by two slabs of hmestone slate 

 from Solenhofen, the counterparts of one another, upon which a perfect impression 

 of a Discophorous Acaleph Avas distinctly visible. The impression made upon my 

 mind by the preservation, through countless ages, of an animal so soft as a jelly-fish, 

 was so vivid, that, though I have never seen those fossils since, I well remember 

 their general appearance. I regret the more, however, that I did not at the time 

 make a sketch of them, since to this day they have remained undescribed ; and, 

 so far as I know, no allusion to genuine fossil Acalephs is to be found anywhere 

 except in the first volume of this work (p. 24), where I mention the occurrence 

 of MedusiB in the limestone of Solenhofen as indicative of the earliest period of 

 the existence of that class upon earth. At the time I saw these fossils, our 

 knowledge of the Acalephs was very scanty ; few good illustrations existed ; and 

 the works of Eschscholtz and his followers had not yet been published : so that, had 

 I even been conversant with every thing then known about this class of animals, 

 I could not have determined to what fixmily they belonged. I earnestly hope 

 that some of the German naturalists, who of late have so largely contributed to 

 the advancement of our knowledge of that class, may be induced by this notice 

 to hunt up those fossils, and publish an accurate description of them with good 

 illustrations, that their close affinity to the numerous fiimilies now distinguished 

 among Acalephs may be ascertained. It is now a matter of great importance, 

 for it may aftbrd indications of the connection between the living types of Aca- 

 lephs and their oldest representatives on earth ; since it has been ascertained that 

 certain Coral stocks, a large number of which occur in the Palajozoic rocks, called 

 Tabulata by Milne-Edwards, and thus far referred to the class of Polyps, are 

 genuine Hydroid Acalephs, while a comparison of another type of Corals, called 

 Rugosa Ijy Milne-Edwards, with the Tabulata, makes it higlily probable that they 

 also are Acalej^hs, rather than Polyps. 



As shown before, the Tabulata, luiquestionably, are Hydroids. Direct evidence 

 to that effect has been obtained by an examination of the animal of Millepora ; 

 and as all the other Tabulata, both living and fossil, have the same structure of 

 their solid Polyparium as Millepora, it is evident that the whole group must be 

 considered as essentially acalephian. As far as the Polyparium of the Rugosa is 



