373 Mr. T. H. Huxley on the Anatomy of the genus Tethya. 



The general structure of the central, cortical, and intermediate 

 portions agreed pretty closely with the description ah-eady given 

 by Johnston. 



1. The central 2307-tion. — This consists of a granular mass in- 

 terpenetrated in eveiy direction by short, cylindrical, transparent 

 rods which form a sort of network. At the margins of the central 

 portion, however, the rods become gathered into bundles, and 

 they are longer and lie parallel to one another. In this form 

 they enter the intermediate substance and form the radii before 

 mentioned. When they reach the cortical substance, the majority 

 of the rods diverge and become spread out ; a few however 

 remain as a bundle, and reach the edge, or even project a little 

 beyond it. 



Besides the bundles, a great number of long, solitary rods 

 traverse the intermediate substance radially. 



The rods are cylincbical, and about 2 jo o*^ ^^ ^^ ^^^^ ^" ^^^' 

 meter. They are all perforated by a very narrow central canal, 

 so as to appear like minute thermometer-tubes. 



2. The cortical substance consists of two zones, an inner and 

 an outer, which pass insensibly into one another at the hue of 

 contact. 



The inner is composed of a mass of thick bundles of a fibrous 

 tissue, so interwoven that a slice presents every possible section 

 of them. The rods penetrate this zone, and a very few of the 

 stellate bodies are found scattered through it. 



The outer zone is dense, granular, and otherwise apparently 

 structureless. Scattered through it are great numbers of crystal- 

 Line spheres beset with short conical spikes. 



3. The intermediate substance. — This consists of a granular 

 substance in which ova and stellate crystalline bodies are im- 

 bedded. 



The ova are of various sizes. The largest are oval and about 

 y^^^th of an inch in long diameter. They have a very distinct 

 vitellary membrane, which contains an opake coarsely granular 

 yelk. A clear circular space about jg^^joth of an inch in diameter, 

 marking the position of the germinal vesicle, is seen in the centre 

 of each ovum, and within this a vesicular germinal spot joVu*^ 

 of an inch in diameter is sometimes visible, although with some 

 difficulty, in consequence of the opacity of the yelk. 



The stellate bodies are about y^y^Q ^th of an inch in diameter : 

 they appear to be of a similar nature to those described in the 

 cortical substance, but they are smaller ; and while the radii are 

 proportionally long, there is hardly any centre beyond that formed 

 by their meeting. 



The granular uniting siibstance is composed entirely of small 

 circular cells about ^^-'o^jth of an inch in diameter, and of sper- 



