326 GRACE MEDES 



Herbst ('06), in his Vererbungsstudien II, as a preliminary 

 to a study of the effects of changes of temperature in hybridized 

 forms, gives a brief summary of the effects of similar changes 

 on the larvae from straight fertilized eggs of Strongylocentrotus, 

 Echinus and Spaerechinus. In Strongylocentrotus, a tendency 

 toward increase in body-length, with arm-length approximately 

 unchanged, gave a slight increase in total size. With Echinus, 

 body-length became less whereas arm-length showed only a 

 slight increase, so that the resulting individuals w^ere relatively 

 smaller. In Spaerechinus, the body-length was also less, but 

 owing to a much greater increase in length of arm-rods the de- 

 veloped plutei were of considerably greater size. In all, he found 

 with increased temperature a tendency toward increased com- 

 plexity of skeleton, as shown by the number of rods and ac- 

 cessory processes, accompanied in Strongylocentrotus by the 

 beginnings of lattice-formation. 



; Peter (08) also subjected the eggs of Spaerechinus granulans 

 and Echinus microtuberculatus to such modifications of the 

 medium as were conducive to more rapid growth, such as in- 

 creased temperature and heightened alkalinity, and found a 

 greater variability, as measured by number of primary mesen- 

 chyme cells, correlated with accelerated development. He em- 

 ployed three grades of temperature, a ' Kaltekultur' at ^ about 

 13° to 16°, a 'Warmekultur' about 23° to 26°, and a 'Zimmer- 

 kultur' between the two. In the warmer cultures variability 

 was increased and was accompanied generally but not always 

 by an increase in the mean number of skeleton-producing cells. 

 A similar effect was produced by increasing the alkalinity, 

 whereas acidity resulted in changes similar to those occasioned 

 by lower temperatures. In none of these experiments, however, 

 was rate of growth, he argued, decreased below that probably 

 occurring under natural conditions since even in his 'Kalte- 

 kultur' the temperature was somewhat above that of the open 

 sea in the region from which his specimens were taken; and in 

 the acid solutions, although rate of development was decreased, 

 it was not less than that of his 'Kaltekultur.' 



