586 KKPOKT OF COMMISSIONER OF FISH AND FISHERIES. 



were the lirst to (leinoiistratc the wide distribution and innumerable 

 abundance of this unicellular calcareous alga, and I agree with them 

 in the supposition that these play a sii;iiiticant part in the biology of the 

 ocean and in the formation of its globigerina ooze. 



3. Murracytea'. — Under this name I may here refer to the very im- 

 l)ortant but hitherto neglected group of planktonic protophytes, Avhich 

 were first discovered by John Murray and described under the name 

 Fyrocysfis (5, p. 533, plate xxi; 6, pp. 935-938). These "unicellular 

 algio" are transparent vesicles, from 0.5 to 1 or 1.5 millimeters in di- 

 ameter, and s])herical, oval, or spindle-shaped in form. Their sim^de 

 continuous cell membrane is very thin and fragile, like glass. It is 

 stained blue l)y iodine and sulphuric acid, and seems to contain a small 

 quantity of siliceous earth. The contents of the vesicle is a vacuolated 

 cell, whose protoplasmic network contains many yellow granules of 

 diatomin. The spherical form {Pyrocystis noctiluca Murray) is very 

 similar in size and form to the common Noctiluca miUaris and probably 

 is very often mistaken for it. I saw these thirty years ago (1860) at 

 Messina, and later (1866) at Lauzarote, in the Canary Islands. 



When John Murray published in 1876 the first figures and careful 

 description, he at first i)laced them with the diatoms, but later (6, \). 

 935) he has, with justice, separated them. He there says of Pyrocystis 

 noctiluca : 



This orgauism is everywhere present, often in enormous masses, at the surface of 

 the tropical and subtropical oceans, where the temperature is not more than 20^' to 21^^ 

 C, and the specific gravity of the oceanic water is not diminished by the presence 

 of coast and river Avator. Pyrocystis shines very brightly; the light comes from the 

 nucleus and is ihe chief source of the diffuse phosphorescence of the equatorial oceans in 

 calm weather. 



Since these unicellular vegetable organisms do not have the char- 

 acteristic bivalve shell or siliceous case of the diatoms, but their cell 

 membiane forms a completely closed capsule, they can not be reckoned 

 with the latter, but must be regarded as representatives of a difi'erent 

 group of protophytes, for which 1 propose the name Murracytew or 

 "glass bladders" {Murra, a name given by the Eomans to a glasslike 

 mineral— fluospar (?) — from wldch costly articles are made.)* 



*In the Atlantic and Indian oceans I have seen great masBes of Murracytea', and 

 have distinguished many s])ecics, Avhich may be regarded as representatives of four 

 genera: (1) J'yroryxUs noctiluca Murray; spherical. (2) J'holocystis eUi2)soides Hkl; 

 ellipsoiil. (3) Mu7'rae!iNti8 fnsiformis Ilkl {I'liroii/Htis fiisiformis Murray); sidiidh)- 

 sliaped. (4) Xectoci/xlin m ii rrayn tia lilil; cylindrical. The J/«rr«r_i//(!s multii)]y, as 

 it a])pears, only by simple division (commonly into two parts, less frequently 

 into four). After the: nucleus, lying eccentrically or against the cell wall, has 

 divided, there follows division of the soft cell body, which is separated from 

 the lirm capsiilclike membrane by a wide 8i)ace (filled with a jelly). Then the 

 membrane bursts, and around the two halves or four tetrads there is immediately 

 formed a new covering. Considered phylogenetically, the Murracytea apjiear as 

 very old oceanic Protophytcn of very simple structure. IVrhaps they ought to be 

 regarded as tbc jinccstr.il form of \\w diatoms, for the biv.alvul;ir sliell of the latt(;r 

 could have arisen by a simide halving of the cai)Hiile of the former. 



