Il8 DAVID D. WHITNEY. 



Cultures containing ten drops of sodium silicate were very 

 difficult to produce and consequently the majority of the experi- 

 ments were carried on with jars containing five drops. Table 

 I. shows the general results of the experiments and Figs. I and 2 

 show the dorsal views of the females from the control jars con- 

 trasted with those from the jars containing sodium silicate. The 

 outline of the skeleton of each female was drawn with the camera 

 lucida with the same magnification. 



TABLE II. 



SHOWING THAT THE FEMALES WHICH POSSESS THE Two ADDITIONAL POSTERIOR 

 LATERAL SPINES IN THE CULTURE MEDIUM CONTAINING SODIUM SILICATE 

 WHEN TRANSFERRED TO CULTURE MEDIUM FREE FROM SODIUM SILI- 

 CATE Do NOT TRANSMIT THE SPINES TO THEIR DESCENDANTS. 



When the females of the Brachionus amphiceros type possessing 

 the posterior lateral spines w r ere transferred to jars of culture 

 medium free from sodium silicate the descendants of these females 

 did not develop the lateral spines but developed into the Brachi- 

 onus pala type. Table II shows the results of such experiments. 



Whether the rotifers were able to take the silicate out of the 

 water in solution or whether the green flagellates first took it 

 up and then the rotifers eating them obtained the silicate for 

 their additional spines is not certain. A few experiments were 

 performed in an attempt to determine this point. Green 

 Chlamydomonas were reared in 150 c.c. culture medium con- 

 taining 5-7 drops of sodium silicate. W r hen the flagellates had 

 become very numerous and supposedly had taken up as much of 

 the sodium silicate as was possible they were removed from the 

 siliceous medium and put into fresh medium free from sodium 

 silicate. Several dozen rotifers lacking the posterior lateral 

 spines were added. Eight days later two thousand females were 



