Aciinaria 



G 137 



The specimens are well preserved in formaline, but are heavily stained with 

 dark greenish brown, so that the internal structure cannot well be seen. The 

 sto' lodseum is visible as a short sac below the mouth. There are two large 

 distinct mouth-lobes, unequal in size. 



Fig. 21. Arachnactis hrachiolata A. Agassiz. The larva or young of a Cerianthus, probably of 

 C. borealis Ver. A very young stage with but two pairs of the tentacles of the 

 outer row (i, ii), and with rudiments of three tentacles of the inner circle ; also traces 

 of 8 mesenteries; much enlarged. Canad. Arc. Exped. C. C. A later stage of the 

 same larva, viewed from opposite sides; three pairs of outer tentacles (i, ii, iii) are 

 now developed, but of unequal sizes; also two pairs of the inner or oral circle, 

 in a rudimentary form; eight unequal mesenteries are visible and also two pro- 

 minent labial lobes, and the stomodaeum. Much enlarged. Drawn by the 

 author. 



Fig. 22. The same. From a very young New England specimen. Much enlarged. By J. H. 

 Emerton. 



These stages do not quite correspond in the state of development with 

 similar larvje previously described, but they appear to be identical with the 

 similar larvae found on the northern New England coast. (See Text Fig. 22, and 

 PI. XXII fig. 4). The latter is probably the larva of Cerianthus borealis Ver- 

 rill, a common form in the deeper waters of northern New England, the Gulf 

 of St. Lawrence, etc., and the only species known from the very northern waters 

 of America, but not yet reported from the Pacific coast. 



For additional details concerning Arachnactis hrachiolata, see G. S. Kingsiey, 

 Description of Cerianthus borealis, Tufts College Studies, No. 8, 1904, with three 

 figures of larvffi from Casco bay. Also J. L. McMurrich, The Genus Arachnactis, 

 Journ Experimental Zoologv, Vol. IX, No. 1, 1910, pp. 159-168, fig. 4, (com- 

 pared with other species). Also Journal of Morphology, Vol. V, p. 147, pi. IX, 

 figs. 9-13, 1891. 



