588 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
kowski first advanced the view that the yellow cells are independent 
unicellular organisms, parasitic alge, which for a time live in the 
bodies of the radiolarians, but after the death of the latter come forth 
and multiply by division. This supposition was confirmed experiment- 
ally by Karl Brandt (24, p. 65) and Patrick Geddes, who explained 
further the nature of their symbiosis, and finally showed the wide dis- 
tribution of the vanthellee in the bodies of numerous marine animals, 
as well as their production of zoéspores (Zodxanthella, Philozodn). 
Whether these are ontogenetically connected with certain “yellow 
unicellular alge” which live free in the plankton, remains to be farther 
investigated. Perhaps also in this group belong the XYanthidea which 
were described by Hensen (9, p. 79) and Mobius (10, p. 124) as species 
of Xanthidium and as “spiny cystids,” spherical cells which reach 1 
millimeter in diatineter, contain yellow diatomin granules, and multiply 
by division. Their thick hyaline shell, which seems to consist of 
slightly silicified cellulose, armed with simple or star-shaped radial 
spines, is characteristic. I find these Xanthidee very numerous in 
the oceanic plankton. Perhaps the siliceous-shelled XYanthidia, which 
Ehrenberg has found so abundantly as fossils, also belong here. 
6. Dictyochee.—The ornamented latticed cases of the Dictyochide, 
formed of hollow siliceous spicules, are often found in great numbers in 
the plankton, pelagic as well as zonary. Although these have long 
been known, both living and as fossils, to microscopists, two very dif- 
ferent views as to their true nature are entertained.* 
Ina preliminary contribution “ On the Structure of Distephanus (Die- 
tyocha) speculum” Zool. Anzeiger, No. 334, one of my earlier students, 
Adolf Borgert, briefly showed that each single case contains an inde- 
pendent ciliated cell. He therefore considered it a new group of Flagel- 
lata (or Mastigophora), for which he proposed the term Silico flagellata. 
The “twin parts” described by me (4, p. 1549) he regarded as a double 
ease which had arisen through the conjugation of two individual 
flagellata. To my mind this new interpretation seems to have very 
considerable probability, although I do not regard it as settled that 
the ciliated cells are the swarm-spores of the Phwodarium. In case 
*Ehrenberg, who in 1838 and 1841 first described the ornamented siliceous skele- 
tons of Dietyocha and Mesocena, called them diatoms and distinguished no less than 
50 species of them, some living, some fossil. Later, at Messina (1859), I noticed, 
inclosed within the ornamented hat-shaped latticed shell a small cell, and on that 
account referred it to the Radiolaria, with reference particularly to the similar 
siliceous skeletons of some Nassellaria (Acanthodesmida). Twenty years later R. Hert- 
wig found a spherical Phwodarium, the surface of whose calymma was covered with 
numerous Dictyocha littlé hats (Dictyocha-Hiitchen), and he therefore believed that 
they must belong to this legion. He compares the single siliceous little hats 
( Hiitchen) with the scattered spicules of the Sphewrozoida. In my Challenger report (4, 
p. 1558) I agreed with this interpretation; so much the more when I myself saw nu- 
merous similar Phecystina (Dictyocha stapedia) living among a similar Phwodaria in 
Ceylon, and found specimens in several bottles of the Challenger collections, espe- 
cially from Station 144, from the Cape of Good Hope (4, p. 1561, pl. 101, Figs. 10-12). 
