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PJtOF. E. W. MACniv’lDE. 
the skeleton of the same arms; and further, tliat the hybrids 
between these two species ai-e of a very variable clmracter, 
so that from them a complete chain of forms can be selected 
leading' from larvte showing purely ])atermil to those showing 
pui'ely maternal characters. 
Steinbriick’s work has not received the attention which was 
<lne to it. It was almost ignored by the next Avorkers who 
<jccupied them.selves with the subject — Doncaster and Herbst. 
Doncaster (4) admits that variations occur in the characters 
exhibited by pure cultures oF Strongylocentrotus and Spluer- 
echinus, but believes them to be relatively so infrequent that 
they may be disregarded, and he bases his estimate oF the 
relative intensity of paternal and maternal influence exhibited 
in the charactei- of the hybrid larvm on the same criteria as 
those employed by Vernon. He ariives at the conclusion, 
however, that the influence of either parent — the fjither, for 
instance — does not vary with the ripeness, inunaturity or 
staleness oF the sexual products, but with the temperature oF 
the water, for he found that he obtained the same re.sults in 
December as in May if he artificially warmed the water used 
For the December cultures. This he explains by stating that 
warmed water causes the stronger larvm to develop rapidlj- 
until they reach the point of development where further pro- 
gress depends on food. Then they die and the weaker and 
more slowly developing larvae survive them, and it is these 
that s h o w th e pater n al i nf 1 u en ce most. In colder water 
the stronger larva) develop more slowly, and hence are present 
at the time when the estimate is made (eight days aftei’ 
fertil isation) . 
Boveri (3) returned to the subject of the characters exhib- 
ited by the bastards produced by crossing S t ro n gy 1 o c e n- 
trotns. Echinus and S ph a) re c h i n us . He maintains that 
the influence of the male parent is visible in the shape, skeleton, 
])igmentation, mesenchyme cells, and sometimes the size of 
the hybrid larva. To this Driesch replied (6), controverting all 
these points exce])t the one concerning pigmentation. 
Herbst, in a most elaborate paper (10), in which he deals 
