GENUS ACTINOPHRYS— ACTINOPHRYS SOL. 239 



into the body of the Actinophrys, when it presented the appearance seen 

 in fig. 4. 



Green food swallowed by Actinophrys sol, ordinarily, in the process of 

 digestion, becomes brown, and the remains are discharged from the surface. 



The common Sun-animalcule presents considerable range in size, the 

 body measuring from one twenty-fifth to one eighth of a millimetre in 

 diameter. Ordinarily it is from one twentieth to one twelfth of a millime- 

 tre, and the rays are from one to one and a half the length of the diameter 

 of the body, but occasionally reach double that length or even more. 



Not unfrequently Actinophrys sol is met with of a dumb-bell-like form, 

 apparently consisting of a pair of individuals as ordinarily seen, united by 

 an isthmus, of variable extent, as represented in fig. 10. The animal in 

 this condition has been considered to be in conjugation, that is to say, to 

 consist of two individuals, which have conjoined for some purpose of a 

 sexual kind. I never happened to have the opportunity of seeing two indi- 

 viduals in the act of conjunction. In all those cases in which I have met 

 with the animal in the duplex state, on closely watching-, they turned out 

 to be cases of multiplication by division. In these instances, the isthmus 

 uniting a pair gradually becomes narrower and longer, and then breaks, 

 leaving the original dumb-bell form as a pair of spherical individuals. 

 During the process of division, the animal glides about less actively, and 

 the rays diverge in the usual manner from each ball, but are absent from 

 the isthmus. Each ball also has its own contractile vesicle, which exhibits 

 the ordinary rhythmical movements. The remains of food may also be 

 discharged, as seen in fig. 10, a, but I have not observed the animal feed 

 during 1 the condition of segmentation. 



Though, as intimated, I have not had the opportunity of observing a 

 pair of individuals of Actinophrys sol actually join and unite into one, I 

 have occasionally met with a specimen of biscuit-shape outline, as in fig. 8, 

 which, gradually contracting, assumed a spherical form, as in fig. 7. In the 

 particular case represented, the specimen, when first noticed, contained four 

 large clay-colored vacuoles, of which all but one subsequently, during the 

 contraction of the animal, discharged their contents. 



On one occasion, having observed an Actinophrys sol of peculiar and 

 unusual appearance, I was led to watch it, and continued to do so at inter- 

 vals from 3 o'clock in the afternoon until midnight, It turned out to be an 



