INVERTEBRATA, CRYPTOOAMIA, MICROSCOPY, ETC. 1027 



centimetre in diameter, and fixed by a point of its periphery to some 

 large marine algal. From a distance it has the appearance of a 

 Nostoc. Exposed to solar light, it disengages oxygen, and the green 

 colouring substance is therefore chlorophyll. 



More closely examined it is seen that the mass is composed of a 

 colourless jelly, studded with isolated green points visible to the 

 naked eye, and sufficiently numerous to give the characteristic green 

 colour to the whole body. It is therefore not a Nostoc. If some of 

 the green points are removed from the gelatinous mass, they are 

 found, when in a sufficiently advanced stage of development, to have 

 a remarkable constitution. 



Each of the small green bodies is nearly spherical, and measures 

 from 0*3 to • 4 mm. in diameter. It is composed of very finely 

 granular and rather dark protoplasm, uniformly impregnated through- 

 out with amorphous chlorophyll. Neither nucleus, vacuoles, nor red 

 eye-spot can be detected, and the membrane which envelops it is very 

 delicate. At one spot which may be termed the pole, the cell bears 

 a tuft of vibratile cilia, attached side by side to adjacent points, and 

 endowed with independent motion. At two diametrically opposite 

 points of the equator is a small indentation in the green matter 

 through which passes a strongly refractive homogeneous protoplasmic 

 band which traverses the membrane, bends towards the pole in close 

 contact with the inferior hemisphere, and divides at the same time at 

 its external border into a delicate fringe composed also of vibratile 

 cilia. Since these cilia coalesce at their base, they are not capable 

 of independent movement. The motion is like a wave which is 

 transmitted gradually from the outermost to the innermost cilium. 

 In their nature and disposition these lateral cilia therefore differ con- 

 siderably fnmi those which compose the polar tuft. At this phase of 

 development there are no cilia either at the opposite pole or at any 

 other point of the surface of the green grains. 



Notwithstanding the movements of these three tufts of cilia, which 

 are often rapid, the entire body is in general immobile. Its centre of 

 gravity is so jdaced that, in a position of equilibrium on the slide, all 

 three groups of cilia are visible to the eye. 



At a more advanced stage, the polar tuft first of all disappears 

 gradually, losing its cilia one by one, which may bo found detached 

 in the surrounding jelly, the pole finally becoming completely bare. 

 Next, the two lateral tufts also disa2)pear, apparently by becoming 

 absorbed in the general pr()t(»i)lasm, this being certainly the case with 

 the band wliich cnnnects them. A membrane, henceforth continuous 

 and smooth at all points, with very sharp outline, now clothes tho 

 proto})lasmic body, which has changed iicither in appearance nor in 

 size, two slight depress'ious at the sides still indicating the position of 

 tho lateral tufts of hairs. 



Subsequently a fissi(m takes place in the mass following tho equa- 

 torial plane, and diviiling it into two halves, each half then dividing 

 a^ain by a division at right angles to the first ; and this process c<m- 

 tinucK until a family of sixteen round(.d cells are formed, surrounded 

 by the primitive membrane. The division and multiplication of cells 



