230 BESSIE NOYES 



day of the egg-laying period and the adult takes a circular 

 path near the edge of the medium; as a result of this course, the 

 eggs are deposited near the edge of the liquid and usually occur 

 in two or three groups. The act of depositing eggs has never 

 been observed, so that it is not known whether these groups rep- 

 resent two or three separate deposits or whether the eggs are 

 deposited singly and the groupings are accidental and the result 

 of the circular path taken up by the mother. In the young, 

 transparent organism the passage of food through the jaws, 

 through the esophagus and back into the body, and finally the 

 excretion of waste products can be traced with ease. About the 

 time of death, however, excretion ceases, movement is confined to 

 the anterior cilia and jaws, and the action of the jaws in grasping 

 food seems to be ineffective. Throughout the entire life-cycle 

 the extrusion of waste products from the body seems much 

 less than the amount of material taken through the jaws would 

 indicate, and during the last two days of the life-period many 

 specimens cease the extrusion of fecal masses entirely. At the 

 close of the life-cycle the organism differs markedly from the 

 adult early in the egg-laying period. 



The organism furnishes, excellent material for a study of the 

 physiological and structural changes accompanying maturity, 

 old age, and death. The transparency of the embryo with its 

 rapid development and the accompanying change in color offers 

 excellent opportunity for a study of the relations of the retention 

 of the products of metabolism, muscular degeneration, and the 

 effects of aging. 



The usual type of egg deposited by Proales is slightly larger 

 at one end, whitish in color, very thin-shelled, and 48 x 80ju in 

 size. The egg increases very little in size before hatching, 

 but a few hours after it has been deposited the outline of the 

 embryo can be distinguished. This outline increases in distinct- 

 ness, and soon the embryo can be seen flexed on itself with the 

 long axis parallel to the long axis of the egg. In over 50,000 

 eggs observed in fresh culture medium, hatching has taken place 

 in all cases within twenty-four hours, with the exception of five 

 individual eggs which appeared to have been slightly injured 



