r)SS KKPOUT OF COMMISSIONER OF FISH AND FISHERIES. 



kowslvi lirst advanced the vicAV that tlie yellow cells are independent 

 unicellular organisms, parasitic algic, wliicli for a time live in the 

 bodies of the radiolarians, but after the death of the latter come forth 

 and multiply by division. This sui>i)osition was coufirnuMl experiment- 

 ally by Karl Brandt (24, p. (m) and Patrick Geddes, who explained 

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

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

 as well as their production of zoospores {Zooxanthella, PhUozoon). 

 "Whether these are ontogenetically connected with certain "yellow 

 unicellular algiE'' which live free in the plankton, remains to be farther 

 investigated. Perhaps also in this group belong the Xanthidca which 

 were described by Hensen (9, p. 79) and Mobius (10, p. 124) as si)ecies 

 of Xanthidium and as " spiny cj^stids,'' 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 Xanthidefe very numerous in 

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

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



6. Dieti/ochece. — The ornamented latticed cases of the Dictyochidw, 

 formed of hollow siliceous spicules, are often found in great numbers in 

 the plankton, pelagic as well as zonary. Although these have long 

 been knowni, 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 of Dis^ep/tanws {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 SUicoflageUata. 

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

 case which had arisen through the conjugation of two individual 

 flageUata. To my miiul this new interpretation seems to have very 

 considerable probability, although 1 do not regard it as settled that 

 the ciliated cells are the swarm-spores of the Phcvodarium. In case 



* Elirenberg, who in 1838 aud 1811 iirst described the oriiiuiiouted siliceous skele- 

 tons of Dictyocha and Meaoccna, 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 coll, and on that 

 account referred it to the Radioluria, with reference particularly to the similar 

 siliceous skeletons of some NaxseUaria{Acanthodesmi(la). Twenty years later R. Hert- 

 wig fcmud a spherical Phwodanum, the surface of whoso calymma was covered with 

 unuK^rous Dirli/ocha little hats (Dich/ocha-IIiitchcn), and he therefore believed that 

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

 (Uiitchin) with the scrattered spicules of the Sphwrozoida. In my fhaUent/rr report (4, 

 p. IwS) I agreed with this iutt^rprctation ; so much the more when I myself saw nu- 

 merotis similar rhfrciislhin {Dictyocha nlapcdia) living among a similar Phtvodaria in 

 Ceylon, and found s)>ecimcnH in several bottles of the ChaUenyer collections, espe- 

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



