ASTERIDiR. 
l^ch, 7 
vascular plexus ; it is continued in one direction into an annular vessel 
(or rather vascular plexus) around the mouth, which gives off radial 
vessels (or plexus) to the arms, in tho other into the dorsal ring- vessel 
(vascular plexus), with its branches to tho intestine and genital organs. 
These vessels which, for the greater part, have hitherto been over- 
looked, are placed, in the arms, in the septa dividing the perihsemal 
canals between the radial nerve and the aquiferous ambulacral canal, 
around the mouth in the membrane separating the outer and inner 
perihsBmal ring-canals ; the “sac-shaped organ,” enclosing the “heart” 
and “ stone canal,” is a continuation of these periha3mal spaces, which are 
on the other hand continued in the perihsemal canals, enclosing the dorsal, 
genital, and intestinal vessels, hitherto commonly confounded with these 
vessels themselves. These perihsemal spaces are further continued into 
the subcutaneous system of cavities between the inner and outer (calcified) 
layers of the skin ; a communication with the common peri^dsceral cavity, 
however, is not discovered. Of the parts considered as nerves, the outer 
cellular portion is a continuation of the common ectodermal epithelium ; 
the thicker, inner, longitudinally fibrillated stratum, though permeated 
by, or enclosed between tho fibrillar prolongations of tho epithelial cells, 
is the true nervous substance. Genital pores are probably present in all 
Starfishes ; they communicate directly, through short oviducts or spermo- 
ducts, with the interior of the genital organs, which are surrounded by 
vascular sinuses ; these are direct continuations of the cavities of the 
genital sanguiniferous vessels. 
Agassiz (1) has republished his researches on the embryology of 
A sterias pallida and herylina, printed several years ago for the intended 
fifth volume of the “ Contributions to the Natural History of the United 
States,” and published (or distributed in advance of the intended volume) 
in 1864 ; the concluding chapter treats of the plan of development of 
Echinoderms generally, defending its homological identity in the various 
types, notwithstanding the modifications which it undergoes in each of 
them ; also the typical agreement between Ctenophorous Acalephs and 
larval Echinoderms, and the impropriety of placing Echinodermata and 
Codenterata in different chief divisions of the animal kingdom. Short 
notes are added referring to investigations of later years. The second 
part of the volume gives a series of beautiful illustrations and descrip- 
tions of North American Starfishes, especially their hard parts, prepared 
by the late L. Agassiz for this volume, but first published now “ as 
showing the systematic value of characters almost completely neglected,” 
and illustrating several genera not previously figured. 
The American Starfishes figured by Agassiz {1. c.) are, Asteracanthion 
herylinus, Ag. (pi. ix.)y Asterias ochracea^ Brdt. (pi. x.), Echinaster sentns 
(Say) (pi. xi.). Crossaster papp>osus (L.) (pi. xii.), Pycnopodia helian- 
thoides, Brdt. (pi. xiii.), LineJeia giiildingi, Gr. (pi. xiv. figs. 1-Q), Aster ina 
folium^ Ltk. {ibid., figs. 7-9), Asterojysis imhricata, Gr. (pi. xv.), Pentacerus 
reticulatus, L. {gigas, L.) (pi. xvi.), Solaster endeca (L.) (pi. xvii.), 
Crihella sanguinolenta (Mull.) (pi. xviii.), Astropecten articulatus (Say) 
(pi. xix.), Luidia clathrata (Say) (pi. xx.). That Solaster and Crihella 
should be placed with Aster inidee, Crossaster, and Pycnopodia, in close 
