AEQUOREA COERULESCENS. 177 



Aequorea coerulescens Brandt. 



Mesonema coerulescens Brandt, '38, p. 360, taf. 5. 

 ? Mesonema dublum Brandt, '38, p. 361, taf. 26. 



Plate 4, fig. ^ ; Plate 35, figs. 3-8. 



Station 4B52 ; 100 fathoms to surface; 1 large specimen, 60 mm. in 

 diameter. 



Station 4655 ; 300 fathoms to surface ; 1 specimen, 12 mm. in <liameter. 



The general appearance of this species is so well represented in Mertens's 

 beautiful figure (Brandt, '38, taf. 5) that no extended account is necessary 

 here. Certain details, however, need slight correction. 



The gelatinous disc is thick, the bell shallow, in the adult specimen about 

 60 mm. in diameter by 20 mm. high. 



Tentacles. — These are rather more numerous than Brandt believed 

 there being from three to six between every two canals, instead of only 

 two as Mertens represented them (Brandt, '38, taf. 5, fig. 5), a total of 

 about four hundred and fifty. As Brandt states, the tentacles are of dif- 

 ferent sizes ; they do not, however, form two distinct series as he supposed, 

 but large and small ones are irregularly arranged (PI. 35, figs. 6, 8). Evi- 

 dently they merely represent different stages in growth, exactly the con- 

 dition that is to be seen in the Atlantic species A. groenlandica L. Agassiz. 

 In addition to developed tentacles there are a considerable number of 

 rudimentary bulbs (PI. 35, fig. 5), which are most numerous on regions of 

 the margin where the tentacles are the least crowded. The tentacular 

 bulbs are long, only slightly swollen, laterally compressed (PI. 35, figs. 6, 

 7, 8), and very closely resemble the bulbs of A. groenlandica. Connected with 

 the inner side of each, at its base, is a prominent excretory papilla (PI. 35, 

 figs. 6, 7, p. ex). These organs are evidently the structures described by 

 Brandt as " tassenformiger, an Gestalt der Cupula einer Eichel nicht 

 nnahnlicher Korperchen " ('38, p. 361). The tentacles are short and 

 become exceedingly slender toward their extremities. In the small speci- 

 men the tentacular bulbs are of the same outline, a fact which has 

 rendered practically certain the specific identification of the specimen ; but 

 the tentacles are much less numerous, there being in all only about one 

 hundred and forty, of which from forty-five to fifty are much larger, 

 and evidently of earlier origin than the remainder. 



12 



