THE BIONOMICS OF CONVOLUTA ROSCOFFENSIS. 429 



of laying the egg-capsule, and it is therefore as possible that these organisms 

 are the result of disintegration of the hinder end of the parent as that they 

 have subsequently migrated from the water to the capsule. 



Fig. 4. — Convoluta roscoffensis (0"2 mm. long) one day old. The 

 specimen was one of a batcii hatched in an egg-capsule laid in a dish with 

 other Convoluta. It has already ingested a grain of sand, a mass of 

 brown algal cells (X), a blue-green alga {Y), and contains in addition a fully 

 formed "green cell " {G. C.) and developing green cells {A and £), three of 

 which form a group obviously arising by subdivision of a single colourless cell. 

 \Vithin these three cells, indicalions of the future chloroplasts are visible as 

 peripheral globules. The grain of sand is enclosed by the wandering cell 

 (PHAG.). 



Fig. 5. — Convoluta roscoffensis one day old. It was placed at the 

 moment of hatching (in sea water with the capsule) into ajar with congo red 

 suspended in the sea water. The figure shows that this Convoluta has 

 ingested two algal cells (Al.) as well as masses of congo red. Tlie acidity of 

 the vacuoles round the latter is shown by the edges of the congo red iiaving 

 taken on a blue colour. 



Fig. 6. — A similar specimen similarly treated with methylene blue. The 

 colouring matter is taken up by the wandering cells (J/. JBL), and has formed 

 a diffuse coloration in the region of the gut. 



Fig. 6a. — The figures a, b, c, p, represent stages in the degeneration of 

 developing green cells within the bodies of young Convoluta bred in dark- 

 ness and fed with litmus, and illustrate a number of experiments. Just 

 liatched Convoluta were placed in darkness on August 24th, 1902, and 

 were drawn on September 4th. Older specimens which had developed a few 

 "green cells" in daylight gave a similar result. The figures show that 

 starting with a typical green cell {A.), continued darkness and starvation 

 induce the breaking up of the chloroplast, the gradual loss of colouring 

 matters, and ultimately the formation of a mere heap of fat globules. Fat 

 globules, also the remains of degenerate "green cells," are seen in Pi, 31, 

 fig. 18. Cf. the text, Section III, p. 393. 



PLATE 31. 



Fig. 7. — An immature but full-grown Convoluta roscoffensis, to show 

 the masses of dark brown granules [X^, X.2, X^), which occur regularly in speci- 

 mens examined immediately after capture. The figure gives a good idea of 

 the appearance of the individuals of sterile patches ; but the brown masses 

 are found iu mature as well as in immature specimens. There is good reason 

 for believing that these brown masses are the discoloured remains of Convo- 

 iuta's " green cells " digested by the gut. The otocyst, eyes, and mouth are 

 also indicated. 



