Anatomy of Gorgonid^. 127 



parallel to that of the axis cylinder. Throughout the remain- 

 der of the ccenenchyma the spicules may occupy almost any 

 position, being placed with their axes at all angles with each 

 other. As before stated the spicules are plainly visible 

 through the ectodermal in\ estment of the zoanthodeme. 



Dr. L. W. Andrews, of the State University of Iowa, has 

 very kindl}" made an examination of the spicules, at my re- 

 quest, in order to ascertain something of their chemical 

 nature. This examination has resulted in some surprising 

 discoveries which are as unexpected as interesting. So far as 

 I have been able to ascerain no competent chemist has here- 

 tofore investigated this subject. 



The points ascertained were as follows: 



ist. The pellicle investing each spicule and covering each 

 prominence on its surface, is an exceedingly thin investment 

 of silica or a silicate. 



Upon placing a few spicules on a slide and applying acetic 

 acid and examining under a microscope, bubbles of gas 

 caused by tlie dissolution of the calcium carbonate, will be 

 seen issuing from the spicules. These bubbles do not arise 

 from all parts of the spicule but seem to issue from a few 

 definite spots or even from one. Evidently the acid can not act 

 on the surface but must find apertures where the surface is 

 broken. Having found such a point of access, the acid vigor- 

 ously attacks the calcium carbonate in the interior. 



If now a drop of dilute hydrochloric acid be placed on the 

 spicules, an increased energy is added to the evolution of gas. 

 If an individual spicule is carefully watched under a micro- 

 scope, the acid will be seen to eat out the interior of the 

 spicule commencing immediately under the pellicle, the out- 

 lines of which now begin to appear following the outline of 

 every tubercle in faint shadowy lines. The interior of the 

 spicule now^ presents a central dark mass surrounded by a 

 perfectly clear space around which can be seen the delicate 

 outline of the pellicle. This central core is gradually con- 

 sumed by the acid, with the evolution of bubbles of gas, from 



