588 REPOliT OF COMMISSIONER OF FISH AND FISHERIES. 



kowski first advanced the view tliat the yellow cells are iudepeudent 

 unicellular organisms, parasitic algre, which for a time live in the 

 bodies of the radiolariaus, but after tlie death of the latter come forth 

 and multiply by division. This supposition was confirmed experiment- 

 ally by Karl Brandt (24, p. 05) and Patrick Greddes, who explained 

 further the nature of their symbiosis, and finally showed the wide dis- 

 tribution of the xanlliellece in the bodies of numerous marine animals, 

 as well as their production of zoospores {ZoUxanthelht, PhilozoUn). 

 Whether these are ontogenetically connected with certain "yellow 

 unicellular algfe" which live free in the plankton, remains to be farther 

 investigated. Perhaps also in this group belong the Xanthidea which 

 "were described by Hensen (9, p. 79) and Miibius (10, p. 124) as species 

 of XantJiidium and as " spiny cystids,"' spherical cells which reach 1 

 millimeter in diameter, 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 Xanthidea' very numerous in 

 the oceanic plankton. Perhaps the siliceous-shelled Xanthidia, which 

 Ehrenberg has found so abundantly as fossils, also belong here. 



6. Bictyoeheie. — The ornamented latticed cases of the Dit'tyochida', 

 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.* 



In a preliminary contribution " On the Structure oi Dlstephanus [Die- 

 iyocha) 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 Flageh 

 lata (or MastUjophora), for which he proposed the term SiUcoJiaiieUata. 

 The "twin parts" described by me (4, p. 1549) lie regarded as a double 

 case which had arisen through the conjugation of two individual 

 jiayellaia. 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 Pluvodarium. In case 



* Ehrenberg, who in 1838 and 1841 first described the oruaiueuted siliceous skele- 

 tons of Dictyocha and Mesocena, called them diatoms and distiugnished 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 XasseUaria ( Acan thodesm ida). Twenty years later E. Hert- 

 wig found a spherical Pha'adarium, the surface of whose calymma was covered with 

 numerous Dictyocha little hats (Dictyocha-Hutchen), and he therefore believed that 

 they must belong to this legion. He compares the single siliceous little hats 

 ( Hutchen) with the scattered spicules of the Spha'rozoida. In my ChaUenyer report (4, 

 p. 1558) I agreed with this interpretation; so much the more when I myself saw nu- 

 merous similar Fhwcystina (Dictyocha stapedia) living among a similar I'ha'odaria in 

 Ceylon, and found specimens in several bottles of the ChaUenyer collections, espe- 

 cially from Station 144, from the Cape of Good Hope (4, p. 1561, pi. 101, Figs. 10-12). 



