392 



H. H. NEWMAN 



The hybrid situation in Echinoids 



A close comparison of the results of hybridization in Echinoids 

 with that of Teleosts has served to place the whole matter in a 

 new Ught and to emphasize the need of further work on Teleosts. 

 It seems necessary in making such a comparison to show graph- 

 ically the interrelations of the species that have been crossed. 

 The following table gives in italics the genera of Echinoids used 

 in all of the various experiments, together with an outline of their 

 classification (table 1). 



TABLE 1 



A goodly number of investigators have crossed Strongylo- 

 centrotus and Sphaerechinus, using a number of species of each 

 genus. Such crosses are of merely intergeneric width and are 

 hardly to be classed as heterogenic. 



Interfamily crosses have been carried out between Echinus of 

 the family Triplechinidae and Sphaerechinus of the family of 

 Strongylocentrotidae, and there is Uttle difference of opinion 

 as to the evidences of paternal heredity. Inter-sub-order crosses 

 between Arbacia of the suborder Arbacina and members of the 

 suborder Echinina have given less definite results as to the 

 hereditary effect of the foreign sperm, Driesch stating that the 

 larvae were pure maternal and Fischel that the paternal influence 

 is shown in form, size, pigment, and skeleton. Neither author 

 was able to rear the larvae far enough to study very definite 

 characters. 



