STUDIES IN CYTOLOGY 403 
4, Blimination of part of the chromosomes and skeleton of inter- 
mediate character. 
Examples: Toxopneustes @ X Hipponoé 2 
Arbacia ¢ X Echinus ¢ (Baltzer) 
Arbacia ° xX Toxopneustes 2 
Toxopneustes ¢ X Arbacia 2 
5. Elimination of part of both maternal and paternal chromo- 
somes and inhibition of development. 
Examples: Arbacia @ x Toxopneustes 2 
Toxopneustes ¢ xX Arbacia 2 
This list of examples is not meant to be exhaustive but is given 
simply as a means of illustration. 
It is evident that in a single series there is a correlation between 
the types of larvae exhibited and the behavior of the chromosomes. 
It is further evident, that taking echinoid hybrids as a whole, there is 
a series of well defined grades, from retention of all chromosomes and 
preponderance of one type over another, through retention of all chro- 
mosomes and a blending of type, to a rejection of more than the half 
number and failure of development. 
It must be pointed out that such examples as Echinus ¢ xX 
Antedon ¢ are in a way misleading to one who does not remember 
that the erinoid larva of early age has no skeleton. We should not 
expect a spermatozoan having no determinant for a skeleton to 
produce much effect in an egg having such a determinant or 
determinants. 
It should further be pointed out that such cases as those coming 
under paragraph 2, e.g., Hipponoé ¢ x Toxopneustes ~ as well 
as the fertilizations of the echinoid egg by the sperm of annelids 
and molluses (Godlewski, ’11, Kupelwieser, ’09), and the fertiliza- 
tion of eggs which have been given a certain impulse to partheno- 
genetic development by means of chemicals, give as these authors 
have pointed out, thelykaryotic larvae. Practically larvae de- 
rived from such crosses inherit from the egg parent alone just as 
strictly as if the eggs had been caused to develop from the first 
by artificial chemical fertilization. 
