

PLANKTONIC STUDIES. 593 



Badiolaria.—Ti^o class of organisms has remained so long uiiknowu 

 to us, and by the brilliant discoveries of the last decade has been sud- 

 denly placed in so clear a light, as the Radiolarla (comp. 4, § 251-2G0), 

 For half a century we knew next to nothing of these wonderful rhizo- 

 pods; to-day they appear as one of the most important planktonic 

 classes.* These, the most varied in form of all the unicellular organ- 

 isms, forni a purely oceanic class, and live and swim in all seas, especially 

 in the warmer ones. ^N'umenms species are also found near the coasts, 

 yet these are not distinguishable from those of the open sea. They 

 constitute no separate neritic fauna. 



'S-'ast crowds of Radiolaria occur at the surface of the ocean, as well 

 as at different depths. Long ago Johannes Midler remarked: 



It is a great plieuomeuon that Araiithomeira can be takeu daily by tlionsaiids in a 

 calm se.1 and independently of storms; and tiiat of many specits of rolycijatina, 

 hnndrcds of individnals were seen during my last residence at the seashore (2, p. 25). 



I have tried myself, on the hundreds of voyages to different coasts 

 which I have made since 185(5, to thoroughly study the natural history 

 of the Radiolaria. The incomparable collections of the Challeru/er 

 afforded me by far the richest material for observation. The results 

 obtained therefrom are embodied in the report (18S7). Among other 

 references to the conditions of the plankton there mentioned, it brought 

 up the following pro])ositions: (1) Badiolaria occur abundantly in all 

 seas which contain a medium amount of salt, and which do not (like 

 the Baltic) receive a sti'ong influx of fresh water. (2) In the colder 

 seas only a few species occur (chiefly Acantharia), but immense quan- 

 tities of individuals; towards the equator the variety in form gradu- 

 ally increases (horizontal distribution, comp. 4, § 220-2.31). (3) The 

 chief groups of Radiohtria are distributed unequally in the five bathy- 

 zones or girdles of depth of the open ocean. The subclass Porulosa 

 (the two legions of S^nmellaria and Acantharia) inhabit especially the 

 two upper zones. On the other hand, the subclass Oscidosa {Nasselaria 



*After Ehreuberg, in 1847, had described the siliceous shells of some hundred 

 species from the Barbados, we obtained in 1858 the first description of their organ- 

 ization through Johannes Miiller. In the Avork with which this great master closed 

 his renowned life he described 50 species which he had observed alive in the Med- 

 iterranean Sea (2). ^Vhen in continuation of this I devoted a winter's residence 

 in Messina to their i'urther investigation, I was able in 1862, in the monograph con- 

 aesiuent thereupon, to distinguish 144 new species, in all 113 genera and 15 families (3). 

 But this rich Badiolaria fauna of Messina still gave no promise of the immense quan- 

 tities of these delicately ornamented creatures peopling the open ocean, and 

 whose variously formed siliceous shells, sinking to the l)ottom after death, formed 

 that wonderful sediment, the "Badiolaria ooze." This was fust discovered thirteen 

 years later by the Challenger. The investigation of the fabulous radiolariau treas- 

 ures (chiefly from the Pacific) which this expedition brought home has led to the 

 discrimination of 20 orders, 85 families, 739 genera, and 4,318 species (4, v) 256). 

 Further study of the Badiolaria slime of the deep sea will bring to light many new 

 forms from this inexhaustibly rich mine. 

 H. Mis. 113 38 



