180 PERCY SLADEN TRUST EXPEDITION 



of the endoderm is recorded by the leaving of the outer half of the radial canal wall 

 in situ alongside the umbrella. In adult specimens the radial canals run alongside this 

 mass of endoderm nearly to the top of the sub-umbrella and there they curve sharply 

 inwards to the stomach. 



Turritopsis nutricula has been well described and figured by American naturalists, 

 and there is no evidence to show that its endodermal peduncle is converted by further 

 development into a mass of cells which block up the upper part of the cavity of the 

 sub-umbrella. Maas (1909) has already said that the differences between the two species 

 may be defined as stages in development, and that is the case, but up to the present 



1 have failed to find any proof that Turritopsis nutricula develops into Turritopsis 

 polycirrha. 



9. Turritopsis nutricula, McCrady, 1857. 



Oceania {Turritopsis) nutricula, McCrady, 1857, p. 55, pi 4. 



Turritopsis nutricula, McCrady, 1858, p. 127, pi. 8, fig. 1. 



Modeeria multitentacula, Pewkes, 1881, p. 149, pi. 3, figs. 7 — 9. 



Turritopsis nutricula, Brooks, 188<i, p. 388, pi. 37. 



Turritopsis nutricula. Brooks and Rittenhouse, 1907, pp. 429 — 460, pis. 30 — 35. 



Turritopsis nutricula, Mayer, 1910, p. 143, pi. 14, figs. 10 — 13, pi. 15, figs. 10 — 13. 



Turritopsis nutricula, Bigelow, 1913, p. 8. 



Locality. Chagos Archipelago, Salomon Atoll, Surface. 5 July, 1905, Q. 



2 specimens. 



The umbi'ella is about as high as broad (:^"5 mm.), with a rounded summit; its 

 sides are slightly curved inwards about the middle and the walls are rather thin. Velum 

 moderately broad. The stomach is large and cross-shaped. The mouth has four very 

 short perradial lips and its whole margin is lined with isolated, globular, clusters of 

 nematocysts. Four fairly broad radial canals. The radial canals on leaving the stomach 

 proper are very wide and have very thick walls, which coalesce, so that the stomach 

 appears to hang from a thick cellular peduncle, about one-third its length. The gonads 

 are interradial upon the walls of the stomach ; one specimen has ova and the other 

 spermatozoa. The tentacles are arranged in a single row on the margin of the umbrella 

 (one specimen with 56, the other with 45 tentacles). They have a smooth, even surface, 

 but are densely covered with minute nematocysts, and terminate with a bulbous 

 enlargement. The basal bulbs of tlie tentacles vary in size, especially in length. They 

 adhere on the outer side to the margin of the umbrella, and the basal half of the inner 

 side is covered with a semicircular loop of nematocysts. There is a small reddish-looking 

 ocellus on the inner side of every bulb, situated close to the tentacle. 



The specimens in the " Sealark " collection are similar to the published figures of 

 Turritopsis nutricula. The formation of the endodermal peduncle is identical with that 

 of Turritopsis nutricula, and not at all like that of Turritopsis polycirrha. 



Bigelow (1913) in his description of Turritopsis nutricula from Japan calls attention 

 to a distinct terminal dilatation of the tentacles, and he points out that similar dilatations 

 also occur in specimens taken on the Ameiican coast at Newport. It is strange that these 

 dilatations have not been previously noticed by the American naturalists. The specimens 



