ATLANT. DEEP-SEA EXPED. 1910. VOL. Ill] 



SCYPHOMEDUSAE. 



Fig. 1. Projections of natural top angles in specimens of Peiyphylla hyacinthina brought home by the "Michael Sars" from the Atlantic. 



The upper row includes only dodecabostrycha-individ\ia\s, the lower row only typical, darkly coloured hyacirithina-individuah, and the 



intermediate row only individuals which according to their pigmentation must be placed between dodecabostrycka and hyacinthina. 



(I: Stat. 51, II: Stat. 80, 111: Stat. 58, IV: Stat. 98, V: Stat. 82, VI: Stat. 19, VII: Stat. 56 and VIII: Stat. 101). Natural size. 



distinct groups might come to view if a large number of 

 individuals were measured. Fig. 1 giving camera-lucida 

 drawings of the topangles of a series of specimens, con- 

 veys some idea of the variations in the proportions of 

 the upper part of the bell, from the furrow to the summit 

 of the umbrella. It is evident that there are no charac- 

 teristic differences between the low bells of what Van- 

 hoffen would call P. dodecabostrycka and the high bells 

 of P. hyacinthina. The biometrical measurements show 

 that the variations are quite regular. 



Lastly the geographical distribution of the "Michael 

 Sars" specimens (see the table) shows no trace of dif- 

 ferent areas of distribution for the two species. 



As a result of our observations we must confirm the 

 opinion expressed by Mayer 1 ) and Bigelow that P. dode- 

 cabostrycha cannot be specifically distinguished from P. 

 hyacinthina, but is merely a synonym. Besides we find 

 no reason for a separation of the two former "species" 

 as biophysically determined variant groups as "forms". 



In addition we may refer to some important results 

 obtained by the "Michael Sars", on the 22nd of May 

 1911 in the Sognefjord. A haul of six hours duration, 

 with the usual arrangement of the apparatus gave the 

 abundant material noted in the table on p. 7. Many of 

 the small individuals must be referred to the group which 

 I have termed intermediate and some to the typical dode- 

 cabostrycha-gwup, although this species has not hitherto 

 been recorded from Norwegian waters. All the specimens, 

 however, really belong to P. hyacinthina representing all 

 stages of development from those 7 or 8 mm in diameter 

 upwards. Although, as stated by Bigelow, the general 



rule is that "in Periphylla the amount of pigmentation 

 increases with growth", there are exceptions.— Thus a few 

 very small darkly pigmented examples of Periphylla were 



Station 



dodecabo- 

 strycha 



intermediate 



hyacinthina 

 typ. 



10 



2 







19 



— 



— 



8 



34 



— 



— 



1 



42 



— 



1 



1 



45 



— 



— 



1 



51 



6 



— 



1 



52 



— 



— 



1 



53 



4 



— 



1 



56 



2 



— • 



1 



58 



1 



— 



— 



62 



— 



— 



4 



64 



2 



— 



1 



66 



— 



5 



— 



67 



1 



2 



— 



70 



— 



1 



1 



80 



4 



16 



6 



81 



10 



12 



3 



82 



— 



3 



6 



84 



— 



3 



— 



88 



— 



1 



— 



92 



2 



— 



— 



94 



— 



- 



1 



98 



— 



12 



— 



101 



— 



2 



3 



Table showing the occurrence of P. dodecabostrycha, 



P. hyacinthina and the intermediate stages at the stations 



of the "Michael Sars" during the cruise of 1910. 



') Medusae of the Hawaiian Islands (Bull. U. S. Fish Comm.), 1903, p. 1137. 



