ELTCOPE DIAPHANA. 



85 



Fig. 123. 



a tendency to be somewhivt rectangular or bottle-shaped (Fig. 121), 

 while the ovaries, when distended with eggs (Fig. 122), are more 

 generally sjjherical ; the number of eggs in an adult female 

 are not nmnerous, not more than twelve to fifteen ; the eggs 

 are quite large, and have a very sharply defined germinative 

 vesicle. The proboscis (Fig. 123) lengthens but little in 

 older Medusa?, almost the only change being the greater 

 mobility of the lips of the actinostome ; the veil is totally 

 wanting in young Medusa^, and in the adult is a very nar- 

 row ribbon round the circular tube, hardly extending beyond 

 the root of the tentacles, so that it easily escapes notice. 



Thi.s Medusa is exceedingly phosphorescent, having a very white 

 brilliant light, which is given out most strongly at the base of the 

 long tentacles. These Medusa? appear as early as 

 March, and are found as late as November. The 

 Ilydrarium (Fig. 124) grows to but little more than 

 an inch in height, and resembles Laomedea genicu- 

 hda ; but the absence of the knee at the base of the 

 sterile Hydra, and the long ringed branch support- 

 ing it, distinguish it at once from that species. The 

 calycle is elliptical, arching regularly towards the 

 centre, and tapering at the two ends (Fig. 125) ; from twelve to 

 fifteen Medusa? develop in each calycle. Found at pig 125. 



near low-water-mark, attached to the base of Fucus 

 vesiculosus. 



It may be that the Medusa of Laomedea genicuJata 

 of Gosse, figured on Plate IV. of his " Devonshire," 

 may prove to be the young of Thamnanfias lucida of 

 Forbes, which is the English representative of our 

 Eucope diajihana. Should this be the case, the two 

 species are evidently distinct, and representative spe- 

 cies in the Acadian and Lusitanian Fauna. Is not 

 the Medusa fimbriata of Dalyell (PI. 52, Figs. 6, 7) 

 the same as the Medusa of Laomedea genicidata, and is it not also 

 identical with the Thaumantlas lucida of Forbes ? 



Massachusetts Bay, Nahant (Agassiz) ; Buzzard's Bay, Naushon (A. 

 Agassiz). 



Cat. No. 78, Nahant, July, 1861, A. Agassiz. Hydromedusarium. 

 Cat. No. 79, Naushon, Sept. 18G1, A. Agassiz. Hydromedusarium. 

 Cat. No. 281, Naushon, Sept. 1861, A. Agassiz. Hydromedusarium. 



Fig. 12.3. Proboscis of an adult MiMlii.sa. 



Fig. 124. Ilycliarium of Eucopi' diapliaiia, natural size. 



Fig. 120. Magnified view of sterile Hydra an<l of a reproduetive calyelo. 



