no Natural History Bulletin. 



mal plate of each mesentery. It forms that part of the gullet 

 situated between the ectodermal lining and the endodermal 

 investment. It is transparent and, as mentioned before, ap- 

 parently structureless, having much the appearance oi formed 

 matter in cartilaginous tissues. It is but little affected b}- the 

 action of acids, seems firm and elastic in substance, and con- 

 tains the cells which elaborate the spicules. 



The basal substance answers well to the description of 

 "conjunctive substance" of the lower animals given by Kol- 

 liker, who describes conjunctive substances as those pertain- 

 ing to the tissues which exist between the internal' and exter- 

 nal epithelium and which are neither muscles nor nerves.^ 



Stellate mesodermal cells. PI. I, fig. 9. These are the cells 

 directly concerned in the formation of spicules. They bear a 

 general resemblance in form to the polar cells iownd in the gray 

 matter of the spinal cord of vertebrates. The prolongations at 

 the poles seem, in certain cases, to anastomose with«those 

 from other cells. I have been unable to entirely satisfy myself 

 as to whether one or several of these cells, contribute to the 

 formation of an individual spicule. 



Water- Vascular System. This consists of a great 

 number of canals of various sizes vv^hich ramify throughout 

 the zoanthodeme and serve to place the various polyps in 

 communication and to conve}'^ to each individual of the com- 

 munity its share of the common stock of food, which is thus 

 evenly distributed throughout the zoanthodeme. 



Primary Canals. These are the large vessels which are 

 directly continuous with the body cavity of the polyps. They 

 are hence lined with endodermal cells. In most species of 

 Gorgonias, these canals form a series of parallel vessels sur- 

 rounding the axis cylinder, the individual canals being much 

 larger than those which will hereafter be described as second- 

 ary canals. In this species, however, a cross section of a 

 branch (PI. I, fig. 6) will reveal the fact that the primary canals 



1 More properly endoderm and ectoderm. 



2 Icones Histologicse, p. 93. 



