346 OBSERVATIONS ON THE CHLORAEMIDAE, 



Grube follows Claparede in his view of the structure in question. 



Langerhans* describes in Brada inhabilis three glands as opening 

 in the neighbourhood of the mouth, a median one, the cells of 

 which contain brown pigment granules, and a pair, in the cells of 

 which are round concretions. 



Studerf describes the unpaired gland as opening in front over 

 the oesophagus. 



Jacquet comments (I.e., p. 373) on the numerous misconceptions 

 to which the dorsal vessel has given rise, and, after quoting the 

 opinion of Claparede, to which reference is made above, goes on 

 to say : — " Nous verrons que Claparede en voulant relever une 

 donnee qu'il considerait comme erronee, retombe dans les idees 

 de quelquesuns de ses predecesseurs, idees que je suis arrive a 

 considerer comme fausses. Cet auteur croit avoir trouve la cause, 

 qui a induit en erreur Costa, dans la couleur de cette glande. Si 

 cette soi-disant glande est plus foncee qu'un vaisseau sanguin 

 ordinaire, cela depend de deux motifs. Comme cet organe pre- 

 sente dans sa partie la plus renflee un diametre de plus de vingt 

 fois celui d'un canal sanguin, il est naturel que contenant une 

 beaucoup plus grand quantite de liquide, celui-ci paraitra plus 

 fonce. En outre, on remarque que les parois de cet organe con- 

 tiennent des elements pigmentes." Further on he conjectures 

 that the anterior dilated part of the dorsal vessel may have a 

 glandular wall secreting a substance calculated to facilitate diges- 

 tion. He thus denies entirely the presence of anything but a 

 thick dorsal vessel or heart with a pigmented and perhaps 

 glandular wall. 



Horstj was the first, so far as I have been able to determine, 

 who gave an accurate account of this structure. He shows that 

 it is the dorsal vessel enclosing in its interior an elongated narrow 



* "Die Wurmfauna von Madeira," 'Zeitschr. f. wiss. Zool.' xxxiv. Band. 



(1880). 



f " Beitrage zur Naturgeschichte wirbelloser Thiere in Kerguelensland" 

 ♦ Archiv fur Naturgesch.' 1878. 



+ " Ueber ein rathselhaftes Organ bei den Chlor?emiden," 'Zool. Anz.' 

 vm. (1885). 



