No. 10. — Bibliography to accompany “ Selections from Embryological 
Monographs, compiled by ALEXANDER AGASSIZ, WALTER Faxon, 
and E. L. Mark.” 
jII.* 
ACALEPHS. 
By J. WALTER 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, Hphyra Eschscholtz, are larval stages of Awrelia 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 by Krohn (A.) in 1855. A similar 
direct development has been discovered by Haeckel (E.) in Aurelia. Important ob- 
servations on the development of different genera of Acraspeda have been published 
by Agassiz (L.), Clark (H. J.), and Claus (C.). 
The segmentation and peculiar delamination of the ovum of the Trachymeduse 
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.), Allman (G. R,), Claus (C.), Gegenbaur (C.), MeCrady (J.), and others. 
Kleinenberg’s account of the embryology of Hydra is the best existing of this re- 
markable genus. 
The Discoidea (Velellide and Porpitide) have engaged the attention of many 
embryologists, among whom are Agassiz (A.), Huxley (T. H.), Kolliker (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 Watrer Faxon. Bull. Mus. Comp. Ziol., IX. 6, p. 197. 
March, 1882. II. Echinodermata. By ALExanpER Acassiz. 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 
