round the Shores of the Island of Bombay. 259 



subject*. Besides red^ spots of white, yellow, green, and brown 

 water have been seen in different parts of the globe ; but those 

 of red and white are most common in the Arabian and Red Seas, 

 and of these two the red will chiefly occupy us here. They are 

 of transitory duration, and, so far as the red colour is concerned, 

 receive explanation from what occurs at our own doors, viz. in 

 the sea-water pools left by the reflux of the tide on the shores 

 of the Island of Bombay. A person casually looking at one of 

 these pools, w^ould say that a quantity of vermilion or minium 

 had been thrown into it ; but, on examining the water under a 

 microscope, the colour is seen to be owing to the presence of 

 red animalcules, whose name is Peridinium. These are not all 

 red, however, for there are many green ones among them ; and 

 the latter are further observed to be but a transitional state of the 

 former. This, then, is the cause of the red colour, and its sudden 

 appearance and disappearance may be explained as follows : — 



During the first or active part of the Peridinium^ s life, its green 

 colour, which depends upon the presence of a substance closely 

 allied to, if not identical with, the chlorophyll of plants, is, with 

 the other internal contents, translucent, and therefore reflects 

 little or no light ; but gradually, as the time approaches for its 

 transition to another state, called the motionless, fixed, or Proto- 

 coccus-form, a number of semi- translucent, refractive oil-globules 

 are secreted in its interior, directly or by transition from 

 starch, the green colour disappears, a bright red takes its place ; 

 this mixes with the oil, and thus the little animalcule finally 

 becomes visible to the naked eye, and the whole of that portion 

 of the sea charged with them, of course, acquires a deep vermilion 

 colour. This colour, however, only lasts for a few days, for they 

 soon assemble together, become individually capsuled, hke Eu- 

 glena viridis, and in this state float on the surface or sink to the 

 bottom in the motionless, Protococcus-form mentioned. Here 

 duplicative subdivision takes place in several of the capsules, 

 producing two or four new ones from the old Peridinium, each 

 of which, on their liberation, may again become capsuled and 

 undergo a further division, and so on, probably, untiL their for- 

 mative force is expended, and they thus pass into dissolution ; — 

 or a litter of diplo-ciliated monads may be developed in a distinct 

 cell in their interior, which may be the product of a true act of 

 generation, or the final formative eff'ort of the protoplasm, — a 

 point to which 1 have already called attention in many of the 

 Algse and Infusoria; while the remainder of the red oil and in- 

 ternal contents which are not required for the nourishment of 

 the monads become liberated with the latter on the bursting of 

 the capsule, and thus dispersed in the water. A further con- 

 * Ann. des Sc. nat. 4 &ei-. Zool. t-. iii. p. 179- 



17* 



