85 



eleven years after I first began to write on the subject. If he wishes 

 for information respecting the others, I shall be ready to give it to him 

 whenever he likes. 



Between April, 187G and April, 1881. a period of five years, I 

 published eleven papers on recent Crinoidea. But in no one of these 

 did I make any reference to Perrier's errors, not even in that »On the 

 Minute Anatomy of the Brachiate Echinoderms(f where I might natur- 

 ally have exposed them in detail, had I so desired. In fact his name is 

 not even mentioned in this paper. 



In 1882, however, after a six years interval, I again ventured on 

 some criticisms of Perrier's work. For I attempted to discuss some of 

 the observations upon the vascular system of Echinoderms which had 

 been ])ublished by the French school and by the German school re- 

 spectively. 



I used these names because they naturally occurred to me when 

 I found that such apparently contradictory results had been obtained 

 in the laboratories of the two countries. The statements of the French 

 naturalists, led by Perrier, rested mainly on the results of injections, 

 and those of the German authors on the section method. Having myself 

 more faith in the latter than in the former mode of investigation, I 

 ventured to suggest the possibility that the connection of the ovoid 

 gland (or supposed heart) with an oral ring might »have been over- 

 looked by the French naturalists''^'. Perrier had totally denied the 

 existence of such a connection in Echinus^'^. But the later researches 

 of Ko ehi er and Prouho, both members of the French school, have 

 conclusively proved that he was quite wrong, and that there is not only 

 a second oral ring i. e. one in addition to that of the water-vascular 

 system which is in connection with the ovoid gland, but also a second 

 set of radial vessels which had entirely escaped Perrier's notice. An 

 important part of my criticisms on Perrier's researches 'which were 

 of the mildest character) has thus been abundantly justified, and I may 

 say the same of my remarks on the earlier work of M. Ko ehler , a fact 

 which Avill be evident to all Avho are familiar with the subject. It will not, 

 I trust, be considered as any breach of confidence for me to state that in 

 July last I had the unexpected pleasure of receiving a most courteous 

 letter from M. Ko eh 1er, in which he acknowledged the justice of some 

 of my criticisms on his researches on the vascular system of the Urchins. 

 For Teuscher's pharyngeal vessels, of which he formerly denied the 

 existence, have since been injected both by Prouho and by himself, 



'2 Quart. Journ. Micr. Sc. 1882. Vol. XXII. New Ser. p. 372. 

 '3 Arch, de Zool. Exp. et Gén. 1875. ï. IV. p. 013. 



