EEPOET ON THE CALCAEEA. 9 



dendroid type. I submitted Leucandra stilifera and Leucandra cataphracta to a careful 

 examination, and can find no essential difference between their canal system and that of 

 Leucetta primk/enia. The distinctions merely concern the size of the flagellated chambers, 

 the average width of the exhalent and inhalent canals, &c, all which is of little consequence. 

 In both cases the constituent parts of the canal system are the same, viz., inhalent 

 canals, flagellated chambers, and exhalent canals, and the properties of these component 

 parts do not differ from those in Aplysilla, Reniera, &c. 



Prof. Hasckel's third type of canal system, called by him "racemose" (" trauben- 

 formig"), corresponds more closely with the reality. This is illustrated by eight diagrams 

 referring to Leucandra ananas (loc. cit., Bd. iii., pi. xl. figs. 1-8). Here we have for the 

 first time in the Monograph to deal with real inhalent canals, flagellated chambers, and 

 exhalent canals. Still, so far as concerns the properties of these three constituent parts, 

 the description is erroneous, as has already been pointed out by Dr. Vosmaer with 

 respect to Leucandra aspera, 1 and Leuealtis solida. 2 



Prof. Efceckel describes his " racemose" type as follows :—" The branch-canals, which 

 proceed from the gastric surface, and ramify centrifugally towards the dermal surface, 

 are in certain places dilated into vesicles, mostly spherical in form, and it is only these 

 swellings or chambers which are covered on their inner surface with flagellated epithelium, 

 this latter being completely absent from all the other surfaces of the canal system." 

 Dr. Vosmaer's observations by no means agree with the description just quoted. He 

 states that the inhalent canals, if ramifying, do so exactly in the opposite direction to 

 that indicated by Hseckel, their communication with the outer world being effected by 

 the dermal pores, and with the flagellated chambers by the pores in the walls of these 

 latter ; that the flagellated chambers each possess in addition to the pores a larger 

 opening by which the water streams into the exhalent canal system ; that these ojienings 

 are of smaller diameter than that of the corresponding exhalent canal ; that, in a 

 word, the canal system of Leucandra aspera and Leuealtis solida is in its chief 

 characters closely allied to that, for instance, of Aplysilla, as described by F. E. Schulze. 4 

 I thoroughly agree with Dr. Vosmaer's conclusions. In addition to Leucandra aspera 

 and Leuealtis solida, I examined Leucandra nirea, Leucandra johnstonii, Leucandra 

 ananas, and in all these cases, as well as in all the Leucones of the Challenger 

 collection, I found the structure of the canal system presenting just the same characters. 

 Nor did I find anything that would indicate a modification resembling the fourth and 

 last type, described by Hasckel under the name of " vesicular " ("blasenformig "), as follows : 

 — " The vesicular type takes origin from the racemose type simply by the extension 

 of the flagellated chambers into larger cavities of irregular outline, which come into 



1 Xirderlcind. Archiv f. Zool, SuppL-Bd. i. p. 148, 1882. 



2 Voorloopig berigt omtrent h. onderzock turn de Nederl. werktafel in li. Zool. Stat, te Napels. Haag(?) 1881, p. 5 

 ' Kalksch-wamme, Bd. i. p. 231. l '/.< Uschr. f. wiss. Zool., Bd. xxx. p. 106, 1878. 



(zool. chall. exp. — paut xxiv. — 1S83.) An 2 



