HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



. The important works of the last fifteen years, mostly 

 based on collections from great marine expeditions, have 

 caused a revision of the classification of the Medusae, 

 but many systematic questions still remain unsettled. The 

 important works of Vanhoffen, Maas, Hartlaub, Browne 

 and Bigelow 1 ) have added so much to our knowledge 

 of the anatomy, ontogeny and classification of the oceanic 

 Medusae that in regard to these points little new could 

 be expected from the "Michael Sars" material, but as the 

 biology of the deep-sea Medusae is still to a great extent 

 enveloped in darkness, as evidenced by recent discussions, 

 this material is likely to fill up many gaps in our know- 

 ledge of the life history of the oceanic Medusae. 



We have long known that surface and deep-sea 

 organisms form two large and distinctive groups of colour. 

 The vivid colours of surface Medusae contrast with the 

 uniform purplish brown or black of deep-sea Medusae. 

 The intensity of colouring is subject to individual variation. 

 Probably Hjort 2 ) was the first to call attention to the fact 

 that among the fishes differently coloured individuals are 

 distributed according to certain rules within the different 

 layers of water, and it was interesting to see whether the 

 Medusae conform to the same rules. This has proved 

 to be the case in regard to the Scyphomedusae. Among 

 the deep-sea Medusae the variation is distinctly correlated 

 to the bathymetrical occurrence, as shown by the large 

 collections of Periphylla hyacinthina and Atolla Bairdi. 

 The more hyaline the individuals the shallower they occur, 

 and on the contrary, the denser the pigmentation, the 

 deeper do the specimens generally occur. On this con- 

 nexion it is noteworthy that the colouring of the smaller 

 individuals is generally less dense than that of the larger 

 ones, and hardly any but small specimens are found near 

 the upper limit of the habitat of the deep-sea Scypho- 

 medusae. 



CORONATA. 



Periphylla Steenstrup. 

 Periphylla hyacinthina Steenstrup. 



Bigelow 3 ) has given a review of the present state of 

 our knowledge as to the specific differences between P. 

 hyacinthina Steenstrup, and P. dodecabostrycha Brandt. 



He points out that recent authors do not agree as regards 

 the limits of these species, so that one might call dode- 

 cabostrycha what another considers hyacinthina. He says 

 the only way to throw light on this question is to examine 

 a large number of fresh specimens. — The "Michael Sars" 

 brought home no less than 128 specimens of Periphylla 

 from the Atlantic belonging to these two species, and this 

 material furnishes a good basis for a discussion of the 

 characters of the species. 



First of all, I wish to call attention to the colour as 

 a specific character. Maas 4 ) in his paper on the Medusae 

 from the cruises of the Prince of Monaco, states 

 like Vanhoffen 5 ) that the pigmentation of P. hyacinthina 

 is denser than that of P. dodecabostrycha, giving the 

 lappets of the former a deeper colour than those of the 

 latter. Bigelow rightly points out that this character is 

 of doubtful value saying: "The extent of the pigmentation 

 does not seem much more valuable as a specific criterion, 

 for not only does, this character vary among Medusae in 

 general, but there is also evidence that in Periphylla, the 

 amount of pigmentation increases with growth". I cannot 

 but agree in this view. In the material before me I have 

 tried to separate P. hyacinthina from P. dodecabostrycha 

 by the aid of their colours, and I have come to the con- 

 clusion that 36 specimens must be referred to P. hyacin- 

 thina and 34 to P. dodecabostrycha while all the rest 

 (no less than 58 specimens) could not with certainty be 

 referred to either of the two being intermediate between 

 them, some approaching the one, some the other, but 

 never corresponding fully with either. The accompanying 

 figures show that the different stages of colours form a 

 uniform and regular gradation, and we must Iherefore 

 endorse Bigelow's opinion that a separation of the two 

 species cannot be based on their pigmentation. 



Vanhoffen (1. c.) has drawn attention to another 

 character which besides the pigmentation, will enable us 

 to distinguish the species, viz. whether the bell is high 

 or low. It might perhaps have been sufficient to refer 

 to the figures in Bigelow's memoir cited above, but I 

 prefer to quote them in full: "We then 6 ) find the pro- 

 portions 7 ) of Periphylla hyacinthina to be 1-9:1, 1-7:1, 

 1-5: 1, and of Periphylla dodecabostrycha 1-55: 1, 1-5: 1, 

 1-2:1." There is according to Bigelow a typical con- 

 tinuity in these figures. It is possible, however, that two 



') Mayer's work "Medusae of the World" was unfortunately inaccessible to me. 

 2 ) "Michael Sars" Atlanterhavsekspedition 1910 (Naturen), Bergen 1911, p. 95. 

 ; ) The Medusae. (Mem. Mus. Comp. Zool. Vol. XXXVII), Cambridge 1909, p. 26. 



*) Meduses provenant des campagnes des yachts Hirondelle et Princesse Alice (Res. Campagne Scicntif. Albert I), 

 Monaco 1904, p. 46. 



■ 5 ) Deutsche Tiefsee-Expedhion, Bd. Ill, p. 23. 



e ) By reducing Vaxhoffen's figures to a common standard. 



') Of the bell; the figures indicate height: diameter of the entire Medusa (without tentacles). 



