30 



PLEUROBRACHIA RHODODACTYLA. 



Pleurobrachia rhododactyla Agass. 



PIcurohrachia rhododactyla Agass. Mem. Am. Acad., IV. p. 314, Pis. 1, 2, 3, 4, 5. 

 Pleurobrachia rhododactyla Agass. Cont. Nat. Hist. U. S., III. pp. 203, 294, PI. 2^ 1860. 

 Beroe pileus Fab. (non Flem., Miill., and Esch.). Faun. Griinl. 1780. No. 354. 

 Cydippe pile us Gov I.T). Hep. Inv. Mass., p. 349. 1841. 

 Pleurobrachia rhododactyla Stimps. Mar. Inv. Grand Manan, p. 11. 1853. 

 Cydippe pileus MoRCH. In Naturhist. Bid. til en Besk. af Grbnland, p. 97. 1857. 

 Pleurobrachia Scoj-esbyi Morch. In Naturh. Bid. til en Besk. af Gronland, p. 98. 1857. 

 Pleurobrachia rhododactyla Packard. List of Animals dredged near Caribou Island. 1863. 



The young Pleurobrachia early assumes an outline resembling the 

 adult ; it is slightly pear-shaped, with two very small protuberances, 

 like buttons, indicating the first appearance of the tentacles (Figs. 

 38-40, t), and has a very large transparent sphere (e) with two or 



Fig. 38. 



Fig. 39. 



Fig. 40 



three granules, as an eye-speck. The first cavity fi^rmed in this em- 

 bryo is a small spherical space (Figs. 38-40, d) near the pole opposite 

 the eye-speck. As this grows larger it becomes elliptical, reaching to 



Fig. 43. 



the base of the tentacular (Fig. 41, t) knob, which now extends, like 

 the handle of a jar, beyond the outline ; this cavity is the digestive 

 cavity, and there is up to this time no sign of ambulacral tubes or cavi- 



Fig. 38. Young Pleurobrachia seen from the broad side. 



Fig. 39. Same as Fig. 38, seen from the narrow side. 



Fig. 40. Same as Fig. 38, seen from below. 



Fig. 41. Pleurobrachia somewhat more advanced, seen from the broad side. 



Fig. 42. Same as Fig. 43, seen from above. 



Fig. 43. Same as Fig. 42, seen from the broad side, older than Fig. 41. 



