380 Dr. E. P. Wright on the Animal 



not fall to pieces ; but the retractile portion, on being subjected 

 to the same treatment, breaks up into a mass of minute indivi- 

 dual spicules (fig. 8). The red colouring-matter would appear 

 not to reside in these latter spicules ; for those that I have exa- 

 mined are colourless, presenting in this a marked contrast to 

 the spicules of Melithcea coccinea, which retain their red or 

 yellowish-red colour after being exposed to the action of the 

 caustic alkali. A second form of spicule is met with in the 

 retractile portions of the tube ; it closely resembles that form 

 of spicule described by Kolliker as occurring in Eunicea fusca 

 (Taf. 18. fig. 19), which I think might be called " shuttlecock." 

 While all the forms of spicules met with seem to occupy cer- 

 tain definite portions of the ectodermic layer, yet there is an 

 evident gradation between them, from the smooth fusiform spi- 

 cule to the most irregularly warty forms, which leads naturally 

 to the inference that all these forms are but different stages 

 of growth, by the aggregation of new calcareous material, 

 until the solid tubular structure so long known to us is at last 

 reached. 



The mouth, which is circular, is distinctly marked, and leads 

 into the stomachal cavity, which is small ; the stomachal 

 cavity is separated by a thin and delicate membrane from the 

 general body-cavity. I have not been able to determine with 

 exactness the number of openings between these tAvo portions. 

 The ovaries are in the general cavity, and are invested by a 

 delicate membrane, which is continued in the form of eight 

 mesenteric slender bands to the body of the tube, as is seen in 



In his ' Icones Histologics, ' Prof. Kolliker, when treating 

 of the hardened connective tissue met with in the Alcyonaria, 

 divides the denser structures into : — 



I. Hard structures which are in substance made up of small 

 isolated bodies of a fixed shape (such as the calcareous spi- 

 cules of Alcyonidas). 



II. Hard structures forming a more or less compact structure. 

 Of these there exist : — 



1. Hard calcareous bodies, either isolated or coalesced to- 

 gether, and in combination with a horny or chalky inter- 

 nodal substance, or occurring alone as coalesced calca- 

 reous substance. (Axis of MelithgeaeeEe, Sclerogorgiacese, 

 and Corallinae.) 



2. Lamellated structures, which may be formed as secre- 

 tions, and which, when calcified, leave, after the removal 

 of the salts, an organic remainder preserving the same 

 outline. Here belong : — 



