250 Th. Mortensen. 



PI. X, Fig. 1 represents the specimen from Stockholm. It is in 

 the stage V, the first pinnulæ and cirri having appeared. The calyx 

 (including arms) measures 5 mm, the stalk ca. 20 mm, but it must 

 have been somewhat longer, as the lower part is wanting, probably 

 ca. 10 joints; the part preserved consists of 35 joints. The calyx 

 agrees with that of H. Sarsii in the corresponding stage (Sars, Crin, 

 viv., PL V, Fig. 6), the radialia II and III have become rather broad, 

 and the oralia have been widely separated from the radialia I. It 

 is especially to be noticed that the oralia have the same shape as 

 in H. prolixa, being concave, with the sides bent outwards. There 

 is no trace of infrabasalia. The cirri are radial in position; they are 

 seen to appear successively (Comp. W. B. Carpenter. Researches 

 on the structure, Physiology and Development of Antedon rosacea. 

 Phil. Trans., 1866, p. 733, PI. XL). The first pinnula appears on the 

 12 — 13th arm-joint. The three upper stalk-joints are conspicuously 

 wider than the rest; these and the two following ones are quite 

 short; in the 6th the part below the primary ring has begun to 

 lengthen, the length of the joints increasing gradually from here 

 (comp. Fig. 1, Pi. X). The primary ring is very conspicuous in the 

 upper joints, these joints being distinctly wider in the middle than 

 at the ends. Also in the fully formed joints, where the ends are 

 widened in the usual way, the middle of the joint is still somewhat 

 prominent (PI. XII, Fig. 6; the figure represents joints No. 30 — 31, the 

 enlargement being the same as in the figures 4 and 7 of PI. XI). 



The specimen from Uppsala, which is attached to a cirrus of H. 

 glacialis, is in stage III, the pinnulæ not having begun to appear. 

 The calyx (including arms) measures 2 mm in length, the stalk ca. 

 5 mm. The oralia are still in connection with the radialia; they 

 are of the usual concave shape. — The number and shape of the 

 stalk-joints I have been unable to observe distinctly (the specimen 

 was fixed to a black plate and could not be cleared in balsam). 

 The length of the stalk is, however, so different from that of the other 

 specimen, as also from that recorded by Levinsen (the stalk of 

 the latter specimen was 14 mm long), that it seems scarcely credible 

 that it would have reached a similar length in a stage corresponding 

 to that of the other specimen. The suggestion is then that it may 

 possibly be the larva of Heliometra quadrata (P. H. Carp.), which is 

 thought by A. H. Clark to be a distinct species. Nothing can, 

 however, be said definitely about this for the present. It should be 

 added that the upper stalk-joints of this specimen are only slightly 

 broader than those below. 



During a stay at the Swedish Zoological Station at Kristineberg 

 (Fiskebäckskil) in January this year (1910) I succeeded in finding a 



