No. 2.] MORPHOLOGY OF THE ACTINOZOA. 147 



both surfaces of the mesogloea, and in the sections are cut more 

 or less obhquely, some being cut almost transversely, and others 

 more longitudinally. From the way they run, however, it is 

 clear that they are really transverse, and their apparent oblique, 

 or even longitudinal direction, is due to the manner in which the 

 mesentery is prolonged up into the angle formed by the column 

 wall and the funnel-shaped disc. Lower down they are not so 

 apparent, and in transverse sections of a mesentery in the gono- 

 phoric region they cannot be made out with certainty, although 

 maceration preparations show their presence. This arrange- 

 ment of the muscles agrees with what the Hertwigs have 

 described for C. membranaceus. 



The mesogloea is differently developed in different regions. 

 It is thinnest in the stomatod^al region, and somewhat thicker 

 in the gonophoric region, being in both these parts almost homo- 

 geneous, and without any cells in its substance. In the upper- 

 most angle of the mesenteries it is much thicker than elsewhere 

 (Fig- 8), and contains cavities, reminding one of the cavities 

 found in the mesenteries of the Zoantheae, except that the con- 

 tents are not cellular as in that group, but consist of a granular 

 substance which does not stain at all with borax carmine. 



As stated above, all my specimens were female. The ova are 

 large, and are imbedded in the mesogloea of the mesenteries, as 

 is well shown in the preparation figured (Fig. 9), where the 

 mesogloeal investment has separated from the ovum at one point. 

 The nucleus is large, and is always eccentric, usually projecting 

 very noticeably beyond the general surface of the ovum, which is 

 packed with densely staining yolk granules. One large nucleolus 

 is always present, but the rest of the nuclear substance in all 

 my preparations is apparently broken down, the nucleus appear- 

 ing as an irregularly shaped space with well-marked walls, con- 

 taining the large nucleolus and a few granules. 



The histological details of the mesenterial filaments I hope to 

 describe fully in a future paper. 



I have not been able to find any mesenterial stomata in C. 

 Americanus . 



Clark University, Worcester. 

 March 11, 1890. 



