The Developement of 



Lageuorliyuehiis aciitiis, J. e. Gray, i828. 



Plates I-III. 



X 



his species of dolphin, so frequently met with on the coasts of northern Europe, was, as is well known, described by 

 J. E. Gray as early as the year 1828. His first description of the animal was not, however, very accurate, and occasioned 

 misapprehension. A more detailed description appeared later (1846), and since that time both the skeleton and the external 

 form of the animal have been the subject of numerous investigations, e. g. by Schlegel, Rasch, Van Beneden, Lilljeborg, 

 Sven Nilsson, Malm etc., the same species having been represented imder difierent names. After Flower's careful inspection 

 of the specimens lying in different museums, it may be looked upon as certain, that Schlegel's Delphinus Eschrichtii and 

 Rasch's D. leucopleurus are indentical with Lagenorhynchus acutus, since I cannot but agree with True 1 8.5) in thinking 

 that Schlegel's statement of the number of vertebrae — namely 91 — must be incorrect. According to True, Prof. Cope's 

 L. perspicillatus and L. gubernator are also identical with L. acutus, a theory which Liitken (82) also advances. 



Concerning the occurrence of this species on the coast of Norway, Prof Collett (79) has made several notes, 

 from which it appears that both in the last and in the present century, there have been large and small takes of this 

 species. It is necessary, however, to be cautious in identifying the species from the reports of fishermen and others, as the 

 name certainly varies with the locality. For instance, in south-eastern Norway, the species in question is called "white-side", 

 but '"springer" on the west coast (according to James Grieg) where the fishermen frequently call L. albirostris "white-side." 



Prof. Rasch's account of the shoal near Drøbak in the Christiania Fjord, in June, 1842, when 22 specimens were 

 taken, is well known in cetological literature. Of these 22, 4 were females, one of which had milk in the mammary glands, 

 though no embryo was observed. The males in this species, as in L. alliirostris, are on an average larger than the 

 females. The one figured by Rasch measured 2.630 metres, and a female measured by the same author was 2.310 metres in 

 length; but these measurements were made, according to Rasch's own statement, from the front of the lower jaw to the 

 extreme point of the tail, and not to the cleft in the tail where the back-bone ends. F. W. True gives the length of tliis 

 species as 2.515 metres. 



On the 9th Nov. 1885, a remarkably large catch was made at Torskøen, Manger, some miles north-west of 

 Bergen, by which Bergen's Museum obtained a hitherto unsurpassed collection of embryos, a number of skeletons, etc. also 

 being preserved. It was Dr. F. Nansen, at that time keeper of the Bergen Museum, and keeper James Grieg in Bergen, 

 who preserved this expensive and valuable collection. 



Embryos of this species had previously been briefly described by Gray and Liitken. The former (76. p. 274) 

 mentions an embryo preserved in the British Museum, which came froru the Faroe Isles; he does not. however, state its 

 length, but mentions the 6 foetal hairs on the upper lip. 



Prof. Liitken (82) in Copenhagen has given detailed measurements and, to some extent, description of two 

 fætuses, one 370 millimetres, and the other 485 millimetres in length. He also mentions one 820 mm. long from Greenland, 

 which he supposes to be L. acutus, and not albirostris, under which name it has been represented. Kiikenthal (58) 

 mentions in his great work, a foetus 41 ctm. in length, of which the skin-colouring is briefly described, and one 45.5 ctm. 

 long, whose hand-skeleton has been subjected to comparative examination. 



Being in possession of so complete a collection of embryos of this species in different stages of developement, we 

 will here give' a series of descriptions of the developement of this Odontocete from the earliest at present known embryonic 

 Cetacean forms, up to the almost full-grown foetus, considering principally the external form-conditions. 



I. The smallest Lagenorhynchus embryo (Tafel Ii, found in the collection at our disposal, measured 8 mm., without 

 doubt the smallest Cetacean embryo hitherto examined. The whole egg, (PI. YI, fig. 1) which was preserved entire, measured 75 mm., 



