380 Ralph S. Lillie 



tary elevation of temperature. In the earliest experiments, eggs 

 were exposed for a few seconds to temperatures supposedly high 

 enough to cause partial coagulation of a portion of the colloidal 

 constituents of the protoplasm. Temperatures of 45°, 50°, 55°, 

 and 60° were allowed to act for periods ranging from 5 to 60 sec- 

 onds. No noteworthy changes followed such treatment; swelling 

 and disintegration resulted from exposure for even brief periods to 

 the higher temperatures. A few eggs showed membranes similar 

 to fertilization membranes after exposure to 45° for a few seconds, 

 and occasionally some cleavages were found. The great majority 

 of eggs so treated died without showing any developmental change. 



Treatment that resulted favorably with Asterias eggs also gave 

 imperfect or negative results w^ith Arbacia. Eggs were exposed to 

 35°' 37-5°> ^"^ 4°°' ^^^ periods ranging from five seconds to 

 two minutes. In the most favorable experiments a few eggs 

 showed membranes and irregular cleavages; but development 

 never proceeded beyond a stage of a few^ cells, and the great major- 

 ity of eggs always remained apparently unaffected. I have also 

 attempted to induce cleavage in unfertilized Arbacia eggs after the 

 artificial production of a fertilization membrane by the method 

 introduced by Loeb, viz: treatment for one to two minutes with 

 a mixture of 3 cc. -^-^ acetic acid and 50 cc. sea-water. Eggs so 

 treated become, as in the case of Strongylocentrotus investigated 

 so thoroughly by Lx)eb, far more susceptible to the develop- 

 ment-inducing action of hypertonic sea-water; but the results after 

 warming to 35° for periods of 20, 30, 40, 60 and 90 seconds, within 

 10 to 15 minutes after membrane-formation, were in no observable 

 respect different from those obtained with the same eggs after 

 simple treatment with acidulated sea-water without warming. A 

 certain proportion of such eggs always undergo cleavage, usually 

 irregular, but development rarely proceeds farther than an early 

 stage of a few cells. 



A striking phenomenon, which I have frequently observed in 

 sea-urchin eggs treated in the above manner with acidulated sea- 

 water, seems entitled to special mention here, namely, the appear- 

 ance of active amoeboid movementsof the egg-protoplasm, at times 

 surprisingly energetic in character. The movement appears most 



