NOTES ON EOHINODERM MORPHOLOGY. 323 



sable des Asteries et la position de Forgaue de meme noni cliez 

 les Oursins/^ 



Let us first endeavour to determine the reasons which have 

 induced Perrier to compare it, not with the ovoid gland of 

 Starfishes and Urchins, with which he has previously told us 

 that it corresponds in structure, but with the stone-canal of 

 these types. The stone-canal of a Starfish or Urchin is gene- 

 rally supposed to be lined by a single layer of columnar epi- 

 thelium, parts of which at any rate are ciliated like that within 

 the water-tubes of a Crinoid, and totally different from the close 

 cellular tissue forming the axial organ. 



Perrier describes the axial organ in the cystid phase of 

 Comatula as "un corps ovoide, dont les grandes cellules sont 

 toujours, sur les coupes, disposees en deux rangees contigues, 

 de sorte que le corps ovoide est plein." 



In the pentacrinoid stage it is said to have "I'aspect 

 d'un double canal dont les deux parties semblent s'ouvrir 

 dans le pharynx." It has almost the same histological 

 structure as in the preceding phase ; while in the mature 

 larva there is the same cellular structure, " mais ses parois 

 se recourbent interieurement en lames enroulees qui rapel- 

 lent d'assez pres les dispositions du canal du sable des etoiles 

 de mer." 



As Professor Perrier has not yet described the stone-canal of 

 a Starfish, it is difficult to know exactly what grounds he has 

 for his opinions. The mere fact that the walls of the axial 

 organ in a young Comatula are plicated like those of the 

 stone-canal in Starfishes, scarcely seems to me a sufficient 

 foundation for the conclusion that a part of the water -vascular 

 system in the latter group is represented in the Crinoid by 

 a structure which is generally considered (outside France) as 

 connected with the blood-vascular apparatus. 



It is curious, too, that this last point should receive support 

 from Perrier's most recent observations. In his previous note 

 he stated that '' Le corps ovoide s'implante, chez la Comatule 

 adulte, sur Fun des planchers horizontaux de I'organe 

 cloisonne." Now, however, he tells us that •'•'cet organe se 



