XXll 
INTRODUCTION. 
separate, and inclose the reproductive organ (/), uniting 
again beyond it into a second mesentery (g), which is 
bounded by the craspedum (h) presently to be described. 
Both mesenteries are full and plaited, especially the cras- 
pedal one. 
The spermatic fluid is discharged in a turbid cloud 
through the mouth, and is diffused through the surrounding 
water (pp. 99, 100). The ova are also discharged through 
the mouth, or through the gonidial grooves (pp. 97, 98, 99). 
The development of the egg is into an infusorium-like 
germ, differing in shape in different species, but always 
covered with vibratile cilia, and freely locomotive. Exam- 
ples of the occurrence of these will be found infra (jpassim), 
and many highly interesting details have been recorded in 
the magnifieent works of Sir J. G. Dalyell. The manner 
in which the development of the Anemone proceeds has 
been illustrated by Dr. Cobbold;* a depression in the 
surface of the globose embryo becomes the general cavity ; 
the edges then become incurved and descend into the cavity, 
forming the stomach ; septa spring from the inner wall, 
beginning from the summit and extending downwards, and 
tentacles bud from around the mouth. Eggs, germs, or 
fully formed young, are discharged indifferently through 
the mouth : in the latter two cases the embryos have passed 
their earlier developments within the general cavity. 
7. Teliferous System. In common with some nearly 
allied forms the Actinaria are furnished with a system of 
armature of most extraordinary character. It is compara- 
tively a recent discovery that their tissues contain exces- 
sively minute bodies, in the form of oblong or oval transpa- 
rent vesicles, which have the power of shooting out a long 
thread of extensive tenuit3^ Wagner first drew the atten- 
tion of physiologists to these organs, though he mistook 
their functions for that of spermatozoa ; an error which was 
participated by Dr. Wyman, in his observations recorded in 
Dana’s magnificent work on Zoophytes. Their true cha- 
racter has, however, been sufficiently established by many 
observers, including Wagner, Erdl, Quatrefages, Kolliker, 
Agassiz, and myself. These bodies I have called cnidce, 
or thread-cells. 
The cnidce, in the Actlnoid Zoophytes, are not confined 
to one organ or set of organs. They are found in various 
* Annals Nat. Hist, for Feb. 1853. 
