506 GILBERT C. BOUKNE. 



noticed and figured (loc. cit., pi. xvii, fig. 7) that in the 

 spicules of. certain Gorgonids the superficial warts and pro- 

 jections were continued through the substance of the spicule 

 nearly to its centre^ as it were by roots, and that these internal 

 prolongations were often forked or branched. 



Kolliker entered at great length into the forms of Alcyo- 

 narian spicules^ of which he distinguished two main classes, 

 the smooth and the warty spicules. The smooth spicules he 

 divided into sphseroids, spindles, lenticular spicules, and 

 cylinders ; the warty spicules into (a) simple spicules, which 

 include spindles, clubs, double clubs, and double sphseroids, 

 double stars, double wheels, double spindles and scales, with 

 several subdivisions of the first four kinds, and into (b) com- 

 posite spicules, subdivided into doublets, triplets, quadruplets, 

 &c. Kolliker also denied the intra-cellular development of 

 Alcyonarian spicules, a mistake which was subsequently 

 corrected by Kowalevsky and Marion and von Koch. 



The spicules of recent Alcyonaria, with the single exception 

 of Heliopora, are, as is well know^n from the work of Kow- 

 alevsky and Marion (23 j and von Koch (16), true spicules. 

 They are formed in certain scleroblastic cells which originate 

 in the ectoderm, and either remain there (some species of 

 Clavularia, Xenia) or migrate into the mesogloea. I have 

 been at some pains to verify previous statements on the subject, 

 and to discover, if possible, the earliest stages of spicular for- 

 mation, and to trace them upwards. 



Whilst working at RoscofF, by the kind permission of M. H. 

 de Lacaze-Uuthiers, I was able to make very satisfactory 

 preparations of Alcyonium digitatum and Gorgonia 

 cavolinii illustrating this point. The specimens were killed 

 in an expanded condition by rapid immersion in a "5 per cent, 

 solution of osmic acid in sea water, were thoroughly washed with 

 distilled water, and stained for twenty minutes with Ranvier's 

 picro-carmine. The expanded polyps were cut off close to 

 their bases, placed in dilute glycerine, and laid open. The 

 ectoderm and endoderm having been removed with a camel's- 

 hair brush, very satisfactory flat preparations were obtained 



