322 MR. G. MURRAY AND MISS F. G. WHITTING ON 



anticipated to confirm this view. Tor this first attempt at giving specific characters, then, 

 we heg indulgent criticism. 



But it may be said that we should first justify our inclusion of the PerLdiniacese among 

 Phyto-plankton. It is no new^ step, such workers at Plankton as Cleve and Schiitt 

 having done it before us. Whether these Dino-Plagellata be reckoned plants or animals 

 — and in the absence of any absolute criterion we do not presume to assign them definitely 

 to either group — they appear to form much the largest ingredient in the great mass of 

 oceanic vegetation away from coastal waters, and in any study of the balance of animal 

 and plant life in the sea their weight is a solid one in the scale. The argument is a purely 

 physiological one, and is open to the criticism that the Peridiniacese may yet be animals 

 effecting for themselves by their own intrinsic chromatophores what the Radiolaria, for 

 example, accomplish by symbiosis with their yellow algal cells. However, this is not the 

 occasion for a discussion of the question, nor does the present limited knowledge of the 

 group justify any definite decision. We have found this form of vegetation predominant 

 on the high seas, and we venture to describe it. 



In some of the names assigned to new species we have commemorated the services of 

 Captains Milner and Kudge, Messrs. JoUiffe and Hindmarch, the officers of ships who 

 have done so much in gathering in our material, and Mr. Blackman, who accompanied 

 Mr. Murray on one of the voyages, and to whose judgment we are indebted. 



It Avas one of our objects to endeavour to discover from examination of the tables, 

 drawn uj) to give the results of each voyage, some evidence of seasonal change. With a 

 seasonal variation of temperature amounting to 5° Pahr. as far south as lat. 18° N., 

 and of course a considerably greater variation farther north, some seasonal change in 

 the Plankton seems inevitable. After a series of comparisons we have come to the 

 conclusion that from the imperfections of the record on some of the voyages, especially 

 those at lowest temperature, we would not yet be justified in stating general results. 

 It will need a much longer series of records to establish any such results. 



PTYCHODISCE^. 



Ptychodiscus, stein. 



The only known species, P. NocHluca, Stein, occurs very erratically in our records 

 from lat. 39"^ N. to lat. 14 S., sometimes very abundant, oftener altogether wanting. We 

 have figured it on PI. XXVII. figs. 5 a, b, in order to show its girdle view, w^hich is 

 lenticular in outline. 



P. Noctihwa, var. fimbriatm. This new variety differs from the typical form in having 

 both projecting margins of the girdle fimbriate (PL XXVII. fig. 5 c). It was obtained 

 by Capt. Turbyne in lat. 41 30' X., long. 11° 10' W. 



GLENODINIEiE. 

 Glenodinium, Ehrenb. 



G. trochoideum. Stein, recorded previously from Kiel haven, occurred once only in 

 our collection (lat. 33' 20' X., long. 43 9' W.). 



