428 F. W. GAMBLE AND FEEDERICK KREBLE. 



EXPLANATION OF PLATES 30 & 31, 



Illustrating Messrs. Gamble aud Keeble's paper ou ''The 

 Bionomics of Convoluta roscoffensis, with especial 

 Reference to tlie Green Cells." 



PLATE 30. 



Figs. 1 and 2 represent the appearances of a colony formed by Convoluta 

 roscoffensis on a beach at Tregastei, Cotes du Nord. Fig. 1 is the average 

 appearance at low-vpater spring tides ; Fig. 2 the extent of the same colony 

 at low-veater neap tides. The figures show that the colony is formed of 

 green patches (each of which is remarkably constant), and tiiat the patches 

 occur high up on the shore and are related to the outflow of the salt springs 

 (sliown in streaks and described on p. 408). It will be seen that the patches 

 are far more extensive at spring tides than at neap tides. The explanation 

 of this phenomenon is given on p. 414'. A diagram of this lunar variation is 

 given on p. 414. The horizontal scale of the figures is -^^^ of llie actual. This 

 colony was kept under daily observation from July to September, 1902. The 

 position and extent of the constituent patches at the beginning and end of 

 this two months' record were precisely the same. 



Fig. 3. — Tliis figure represents the egg-capsule of Convoluta roscoff- 

 ensis and the organisms which infect it. A is the capsule with its eggs. 

 jB. a capsule with the embryos just hatching out. C. Linear masses of 

 a colourless refractive spore-like organism. They possess a definite wall, 

 which, however, gives no cellulose reaction with Schutze's fluid. The contents 

 exhibit active movement. The average diameter of these spherical granules 

 is 5 fi, the smallest 2"5/i. D. Spherical colourless cells 15 — 45 /x in diameter, 

 the contents of which are granular, spongy, or heart-shaped in surface view. 

 These cells have no definite wall. E. Active ciliated organisms 20—30 (m 

 long, and filled with refractive, often green globules. F. Pale green cell- 

 colonies 25 /i in diameter. G. Spores with a thick wall containing a finely 

 granular plasma and a mass of refractive globules. When extruded the 

 globules swim actively by one or two flagella. IJ. Brown algae of a dumb- 

 bell sh'ipe and provided with several distinct peripheral chloroplasts. A'. 

 Diatoms. L — Q. Part of a filamentous algal thallus found by the authors on 

 one occasion attached to a Convoluta egg-capsule. It possesses peculiar 

 clear terminal cells, and bifurcated structures at the apex of empty cells. 

 The object of introducing these figures is to einpha&ise the diflicully of 

 obtaining larval Convoluta free from infecting organisms. Many of these 

 structures {G, IJ, A', C) arc to be found in the body of the parent at the lime 



