CKKIAXTHARIA. 



35 



6i4i'N., 10 17' W., 625 fathoms, 14.8.1895, 81.42, Ingolf-Exp., 3 ex. (A). 

 Locality : 



61 42' N., 9 36' W., 545 14. 8. 1895, St. 44, i ex. (B). 



The specimens found were in the following stages of development. 



A,. Stage with ti marginal tentacles, of which the 5th from the directive chamber on the 

 right side is larger than the one on the left, which is very small. The 4th couple of marginal ten- 

 tacles in course of formation. 



A 2 . A little later stage than in fig. i (Nordisches Plankton (XI, p. 71), on the right side how- 

 ever is a small 5th tentacle in a rudimentary stage. 



A 3 . The directive tentacle of the marginal tentacles not yet in formation. 4 marginal ten- 

 tacles on the right side, of which the one nearest the multiplication chamber is small: on the left 

 side 3 large ones and signs of a 4th by the multiplication chamber, 4 labial tentacles arranged in 

 couples. (The earliest known stage of A.albida, reproduced in Nordisches Plankton XI, p. 7, fig. i a). 



B = A,. 



With respect to the animal's exterior, such exhaustive descriptions have already been given 

 by a number of writers, that there is no need for me to go into the subject in detail. I have investi- 

 gated however in a large number of instances (169), principally from the Valdivia Expedition, the 

 arrangement of the tentacles. Though I intend later to give a full account of the results in tabular 

 form, I will nevertheless mention here the following ascertained facts, which corroborate van Bene- 

 den's observations. 



(1) From the 4th to the 6th couple inclusive of the marginal tentacles the right tentacle in 

 each couple begins to form before the left (the animal being viewed with the oral side upwards and 

 the directive chamber turned away from the observer). 



(2) From the third to the fifth couple inclusive of the labial tentacles the same facts are obser- 

 vable as with the marginal tentacles (see i). 



(3) The directive tentacle of the marginal tentacles appears only after the 4th couple of marginal 

 tentacles has appeared, commonly before the 5th tentacle on the right side: sometimes it appears 

 simultaneously with it. 



(4) In no instance are labial tentacles developed above the directive chamber and the contiguous 

 chamber on either side. 



Anatomy. The anatomy has been closely studied by Vogt (1888), Vanhoffen (1895) and later 

 more thoroughly by van Beueden (1908). But even the last account needs no little supplementing, 

 and specially so in the case of the stomatodaeum and its differentiation, and also of the mesenterial 

 filaments and mesenterial musculature. 



The stomatodaeum is very long with a sharply differentiated siphouoglyph, to which at least 

 2 and more commonly (in larger specimens) 3 couples of mesenteries are attached. The hyposulcus 

 is very long and increases in length as the animal grows larger. Vanhoffen has given a good 

 figure in his work (fig. 4, pi. i, 1895) of the hyposulcus. The hemisulci are small in younger examples, 

 in older ones they seem to disappear entirely in proportion as the hyposulcus increases. In one large 

 specimen with 20 mesenteries the directive mesenteries went as far down as to the lower border of 

 the hyposnlcus. 



5* 



