No. 10. — Bibliographj to accompany "Selections from Embryological 

 3Ionograplis, compiled hy Alexander Agassiz, Walter Faxon, 

 and E. L. Mark." 



III.* 



ACALEPHS. 



By J. Walteu Fewkes. 



The most significant of the early contributions to the embryology of the Acra- 

 speda was the recognition by Sars (M.), in 1853, that the sessile genus Scyphistoma 

 Sars, and the free medusa, Ephyra Eschscholtz, are larval stages of Aurelia aurita. 

 The importance of this discovery was much enlarged by Steenstrup (Joh. J.), who 

 pointed out in 1842 that it was an example of "alternation of generations, " similar 

 to that described by Chamisso in Salpa, The development of genera of Acraspeda 

 without a fixed larval stage was first described bj'^ Kiohn (A.) in 1855. A similar 

 direct development has been discovered by Haeckel (E.) in Aiirclia. Important ob- 

 servations on the development of different genera of Acraspeda have been published 

 by Agassiz (L.), Clark (H. J.), and Clans (C). 



The segmentation and peculiar delamination of the ovum of the Trachymedusse 

 have been studied by Fol (H.) and Haeckel (E.). The larval forms of the same, 

 more especially of the commensal genus Cunina, have been investigated by Gegen- 

 baur (C), Haeckel (E.), McCrady (J.), Miiller (F.), Schultze (F. E.), and Ul- 

 janin (B.). 



Dalyell recognized the "planula" among the Hydroida. The production of the 

 free medusa known as the gonophore from the fixed hydroid by an asexual method of 

 gemmation was traced by Dujardin (F. ) in 1848. The knowledge of a wide distribu- 

 tion of this phenomenon among other genera, and its identity with the method of 

 growth called "alternation of generations," we owe to the researches of Agassiz (A.), 

 Agassiz (L.), AUman (G. R.), Claus (C), Gegenbaur (C), McCrady (J.), and others. 

 Kleinenberg's account of the embryology of Hydra is the best existing of this re- 

 markable genus. 



The Discoidea ( Vclellida; and Porpif.idcc) have engaged the attention of many 

 embryologists, among whom are Agassiz (A.), Huxley (T. H.), Kblliker (A.), Pagen- 

 stecher (H. A.), Stuart (A.), and Vogt (C. ). Gegenbaur (C.) first followed the seg- 

 mentation of the egg and the early larval stages of Diphyes, and Leuckart (R.) 



* I. Crustacea. By Walter Faxon. BuH. Mus. Comp. Zonh, IX. 6, p. 197. 

 March, 1882. II. Echinodermata. By Alexander Acjassiz. Ibid., X. 2, p. 109. 

 August, 1882. 



This bibliography extends to the year 1883 inclusive. Simple descriptions of 

 new hydroids, which add nothing to a knowledge of embryology, are omitted. An 

 asterisk [*] before a title denotes that the work has not been seen by the compiler. 

 VOL. XI. — NO. 10. 14 



