THE GREEN OELLS OF CONVOLUTA ROSCOFFENSIS. 201 



during a lunar month from a certain patch of Couvoluta, 

 The samples were taken just after the tide had loft the patch 

 — i. e. immediately after the sojourn of the animals in dark- 

 ness below the surface^ and again after their spell of isolation, 

 just as the tide was about to cover them. 



The animals were fixed on glass slides, decolorised, stained 

 with potassium iodide-iodine, and the amount of starch esti- 

 mated by the resulting coloration. 



The records obtained (Table V) during August, 1905, exhibit 

 a bi-monthly periodicity in the amount of starch present in the 

 animal. The amount is large during the spring tides and falls 

 off during the slack tides. The result is perhaps susceptible of a 

 simple explanation. For during the spring tides low water, and 

 consequently exposure of Convoluta to light, occurs about the 

 middle of the day (and night), whereas during the neap 

 tides the exposure to light takes place during the early 

 morning and late afternoon. Consequently, though the 

 number of hours of daylight to which Convoluta is exposed 

 may be actually greater during the slack tides than during 

 the spring tides, the animals are exposed to a higher light 

 intensity (of the mid-day) during the spring tides than during 

 the neaps. Hence it seems rensonable to suppose that photo- 

 synthesis will be more active during the spring tides, and 

 that this greater activity will be recorded by the larger 

 deposit of starch. It is worth noting — though aside from 

 the question under consideration — that the periodicity of 

 egg-laying by Convoluta receives some explanation from the 

 foregoing; for the egg-laying periods, occurring soon after 

 the spring tides, follow closely on periods of abundant 

 nutrition. Returning to the question, Does the animal 

 receive a share of the carbohydrate elaborated by the green 

 cells ? we have just seen that on this hypothesis periodicity 

 of egg-laying receives a simple explanation. But conclusive 

 evidence is derived from observation of the rates of growth 

 of recently infected Convoluta. The rapid increase in the 

 numbers of green cells in the body — from one or two to 

 thousands — is accompanied, not by any diminution of the 



