22 ralph e. wager. 



Extrusion of the Egg. 

 As previously noted, the egg begins by a process of coales- 

 ence, which may take place in more than one place, so that there 

 may be three or four eggs growing on the same animal at the 

 same time. In such cases the growing eggs form a thick band 

 entirely surrounding the animal, and, in some cases, almost all of 

 the upper third of the body. In other cases but one egg develops, 

 when it appears as a well pronounced dome-shaped elevation, 

 from which, before maturity, pseudopodial processes radiate out- 

 ward, and may encircle over a half of the circumference of the 

 body. In either case the completion of the process of appro- 

 priation of the nourishing cells is marked by the disappearance 

 of the pseudopodial processes, and it then becomes more regular 

 in outline, and more pronouncedly dome- shaped (Fig. 28, PI. IV.). 

 The ectoderm is then ruptured and quickly withdraws over the 

 egg giving rise then to the bowl-shaped depression, or, if the ex- 

 tent of the area occupied by the egg or eggs makes this process 

 impossible, the ectoderm is ruptured and the egg mass flows out 

 through the opening gradually taking on the spherical shape and 

 the shrunken ectoderm again forming the bowl-shaped depres- 

 sion in which the egg is found always to lie. The whole process 

 rarely occupies more than two minutes and is sometimes accom- 

 plished even more quickly. The egg is attached to the body by 

 delicate filaments continuous with the egg membrane. 



Fertilization. 

 The process of fertilization has been described by Brauer ('91^) 

 and to his account little can be added. Unless the process is 

 effected within a few hours after the extrusion of the egg, it 

 becomes vacuolated and increases greatly in size, and finally goes 

 to pieces. Numerous eggs were observed which, thus enlarged, 

 gave ofif a part of themselves after the fashion of budding yeast. 

 These parts thus set free were sometimes as much as one third the 

 volume of the egg. Some eggs were found to be infested by a 

 protozoon which fed upon the egg material. The interior of the 

 egg in such cases contained hundreds of them. Apparently 

 vigorous eggs were not found to be so attacked, but those in 

 which degeneration was going on were frequently infested. It is 



