292 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
This statement will become much clearer by a few illustra- 
tions. Figs. 78-80 are (five-days-old) plutei of purpuratus 
produced by artificial parthenogenesis. They are identical 
ha 
Fig. 78 Fig. 79 Fig. 80 
Fics. 78-80.—Five-days-old plutei of S. purpuratus, produced by artificial 
parthenogenesis. 
with the pure breed of purpuraius. Figs. 81-83 are three plutei 
produced by fertilizing the sea-urchin egg (purpuratus) with 
the sperm of the starfish. They are identical with the plutei 
produced by artificial parthenogenesis. 
Fig. 81 Fig. 82 Fig. 83 
Fics. 81-83.—Five-days-old plutei from S. purpuratus ¢ and Asterias ¢. 
The plutei are identical with the parthenogenetic plutei. 
If, however, the egg of S. purpuratus is fertilized with the 
sperm of S. franciscanus, a closely related form, a pluteus of 
an altogether different type is produced (Figs. 84-86). The 
skeleton has the rough appearance of the franciscanus pluteus 
and the typical arm formation characteristic of this paternal 
form. It is therefore obvious that heterogeneous hybridiza- 
tion is in reality artificial parthenogenesis with this difference 
