Echinoderm Hybridization. 129 



Temp. Temp, 



Herbst's Table XII, g— j^ 1 1° to 19° C. 23° to 29° C. 



Anal ann rods with i root 35 6 



Anal arm rods without lattice structure 25 3 



Anal arm rods with 2 roots 54 36 



Anal arm rods with 3 roots 9 38 



Anal arm rods with 4 roots i 11 



Anal arm rods with 5 roots o 7 



Anal arm rods with 6 to 7 roots o 2 



It will be seen at once that in temperatures of 23° to 29'' C. there is 

 a greater number of plutei and a greater number of arms with lattice 

 structure than in temperatures below 20° C. Similarl}^ the influence of 

 higher temperatures in increasing the number of roots will be noted. 



We have already seen the influence of temperature on pure forms. 

 We may now interpret the pure form and cross-fertilization results. 



1. SphcBrechinus 9 X Strongylocentrotus o" and Sphcerechinus $ X 

 Echinus d^, through abundance of beginnings of lattice formation and 

 greater number of crossbars, show in the warmth, on an average, more 

 resemblance to the mother than to the father. 



2. We can not say that warmth causes this, since in pure Sphcerech- 

 inus larvae also the number of crossbars is raised in the warmth. 



3. Similarly for the anal arm roots, Sphcerechinus ^ X Strongylo- 

 centrotus (^ wannth plutei are more like the mother than are the cold 

 plutei. We can not make a similar assertion for the Sphcerechinus ? X 

 Echinus (S^ plutei. 



4. In both combinations it is impossible for us to speak with respect 

 to the number of arm-bar roots, of a proportionally strong resemblance 

 to the mother. 



5. Plutei of the Sphcerechinus'^ X Strongylocentrotus cj^ have body 

 proportions like the mother, but we can not speak of a stronger appear- 

 ance of maternal body proportions in the higher than in the lower 

 temperatures. With the Sphcerechinus $ X Echinus c? combination 

 we can not assert even the first. 



6. The average body length of the Sphcerechinus $ X Strongylocen- 

 trotus (d hybrids is swung more toward the maternal side in the warmer 

 than in the colder temperatures. 



7. We have recognized a second example of such oscillation in the 

 combination Sphcerechinus 9 X Echinus <S^, where the maternal charac- 

 ters, with respect to body length, become prominent in the cold. 



8. In the pairing of sea-urchins with one like character, there may 

 appear in the descendants a weakening of this character. 



Herbst's conclusions regarding the influence of temperature at 

 different times are of importance: 



1. In order to obtain an increase in fenestrated rods it is immaterial 

 whether we expose the unfertilized eggs, or the blastulse without mesen- 

 chyme, to the higher temperature. 



2. It is not sufficient for increasing the number of larvee with lattice 

 structure, if we. expose the germs only temporarily to the warmer tem- 

 perature and then carry them back. The higher temperature must be 



9 



