INITIATION OF DEVELOPMENT IN CH/ETOPTERUS. 53 



formation of the peri-vitelline space, takes place at the same 

 time. The experiments performed with reference to a deter- 

 mination of the factors operating to bring about these phenomena 

 were too scattered to do more than suggest further lines of work. 

 A few of the findings are interesting, however, in their possible 

 bearing on the behavior of other eggs which do not go through 

 their development in precisely the same way. 



No membrane forms in Chcetopterus as a result of fertilization, 

 but a space arises between the egg and the vitelline membrane 

 already present, as soon as the egg is put into sea-water. The 

 cortical changes involved are comparable to those concerned 

 in the formation of the fertilization membrane in Echinids, yet 

 the development in Chcetoptems ceases with the formation of the 

 first maturation spindle, and all eggs, unless given some further 

 treatment, undergo degenerative changes. The cortical changes 

 which accompany the formation of the membrane induce only a 

 brief period of activity, and do not lead, of themselves, to de- 

 velopment. Loeb ('09) has said that in the sea-urchin in many 

 cases the cytolysis which is started at membrane formation leads 

 to the death of the egg unless checked by a second agent. It is 

 possible that in Chcetopterus also the death of the egg after mem- 

 brane formation is due to cytolysis set up at the time of membrane 

 formation. But it seems more probable that the changes which 

 accompany membrane formation in Chcetopterus represent only a 

 certain part of those which accompany the process in Echinids, 

 and therefore the same results do not follow in both cases. 



The experiments indicate that various salts have a definite effect 

 upon the eggs, e. g., in n/2 sodium chloride or 11/2 potassium 

 chloride the eggs form apparently normal spindles, whereas in n/2 

 calcium chloride and n/2 magnesium chloride they do not. Mag- 

 nesium chloride induces the formation of fairly normal membranes, 

 whereas neither potassium chloride, sodium chloride nor calcium 

 chloride bring about this result. But neutral paraffin oil also 

 induces normal spindles, and Chcetopterus body fluid gives normal 

 results in all respects, in a certain proportion of eggs. Therefore 

 it is evident that no one specific chemical agent is necessary for 

 this first reaction of the egg, but that it may be induced in a 

 number of different ways. It is possible that the changes are 



