OCR Text |
Show 1886.] MR. R. COLLETT ON BAL.ENOPTERA BOREALIS. 2f)9 The corpus emerges almost without any transition from the neck, and has a length of about 19 millim., making the animal's total length about 25 millim. It is perfectly cylindrical, and has a regular breadth of about 3 | to 4| millim., which is thus to the total length as 1 to about 6|. Males and females were intermixed and seemed to be present in equal numbers. The two sexes do not appear to differ in length, colour, or general appearance ; though the males were at the first glance distinguishable on account of the two projecting folds in the skin encircling the outer orifice of the genitalia. The females were all full of myriads of eggs : these were of normal structure, and measured about (H35 millim. in length; no trace of the row of spines which appears on the head of the embryo of the other species could be found when magnified 600 times. Neither were spiral threads to be seen, as described in Echinorhynclmsproteus (Zeitschr. f. wiss. Zool., Bd. xiii. p. 418). It cannot of course at present be stated whence B. borealis obtains the larvse of E. ruber. As the species is decidedly different from E. brevicollis, described by Malm from B. sibbaldi, it is not probable that both species get their parasites from the same crustacean. W e know that Euphausia inermis (a Thysanopod) is the species from which B. sibbaldi probably exclusively obtains its food in the summer months, and it is therefore not improbable that Echinorhynchus brevicollis passes through its first stages with this species. Whether Calanus finmarchicus is the first host of E. ruber can only be conjectured as a possibility. It seems, however, more probable that a somewhat larger crustacean, which perhaps constitutes the food of this Whale at other seasons of the year, is the true transporter of this parasite. Its diagnosis will be as follows :- E. R U B E R , n. sp. Total length 25 millim.; proboscis with about 4 rows of spines, rostellum with 10-12 rows. Neck shorter than the transverse diameter of the body, thread-like. Corpus short, emerging abruptly from the neck. Colour in adult brick-red. XL Time of Capture. It has been previously stated, that in 1882 B. borealis first became the object of general capture, especially at the newly founded establishment at Soroen, near Hammerfest, and it appears to " close the- land" about there every year, although in varying numbers. In previous years the first specimen, according to Capt. Bull, was captured in the beginning of June. The 24th of June was about the best period for catching them, while after the 8th July they gradually disappeared, when other species generally appeared (B. musculus and B. sibbaldi). This year (1885) B. borealis coasted the land along the whole of Finmark, and formed such a considerable portion of the " Fishery," that it surpassed the number of all other species combined. |