134 ACTINOZOA. 



in radii, along the base and disc. Their arrange- 

 ment is best seen in living, semi-transparent 

 species, without any recourse to dissection. 



Thus, a number of imperfect chambers are 

 formed, all opening into one another below, or 

 beyond the free edges of the mesenteries ; and, in 

 some cases, apertures occur in the sides of the 

 mesenteries themselves by which a further com- 

 munication is kept up. These apertures usually 

 appear in the midst of the wide upper portion of 

 the mesentery, not far from the under surface of 

 the disc. They are most constant in the primary 

 partitions ; the secondary mesenteries being fre- 

 quently imperforate. The tentacles, which are 

 hollow, and, in many Actiniae, perforate at their 

 free extremities, open directly into the somatic 

 chambers. 



To the faces of the mesenteries are attached 

 the reproductive organs, which occur as thickened 

 bands of a reddish tint, containing ova or sper- 

 matozoa. The male and female organs appear 

 perfectly similar, previous to examination of their 

 contents. Most Actiniae are dioecious, but, by no 

 external character can the individuals of both 

 sexes, which seem to be about equally numerous, 

 be distinguished from each other. Accurate obser- 

 vations are yet wanting on the reproduction of 

 Actinia, It is probable that the spermatozoa, 

 first diffused in sea-water, find their way through 

 the mouth to the ova contained in the general 

 cavity of the bod}^ 



A long convoluted cord, or ' craspedum,' arises 

 in front of the reproductive apparatus, along the 

 free edge of each mesenter}^ In addition to the 

 craspeda, other organs of similar structure, termed 



