Embryology. 845 
tion, in which the terminology of Diptera is given; then follows 
an analytical table of families, and, except in the case of the Nema- 
tocera and Muscide, tables of genera are also given. There is 
appended to the work a Bibliography of the species described since 
the publication of Osten Sacken’s catalogue. The whole forms a 
very convenient manual, and it cannot fail to stimulate the study 
of this much neglected order. 
EMBRYOLOGY.! * 
OTES ON THE DEVELOPMENT OF HoLoTHuRIA.—The fol- 
me eighth day it is longer than the oral tentacles. About this time 
à favorite attitude of the larva is to erect itself on the posterior 
* Edited by Prof. Jno. A. Ryder, Univ. of Penna., Philadelphia. 
