TRANSACTIONS OF SECTION D. 495 
beyond metamorphosis, it has been possible to observe these conditions in this 
work, ‘The early and variable larval characters have been discarded in fayour 
of definite ones developed by the late plutei. 
The forms used for the hybridisation were the three English species of 
Hchinus, ‘The characters studied in the larvee were as follows ; The late pluteus 
of /. miliaris has no posterior epaulettes, but has a pair of green pigment-masses 
in the anterior epaulettes. On the other hand, the plutei of 7. esculentus and 
4, acutus possess a pair of posterior epaulettes, but lack the green pigment. 
H, esculentus and HL, acutus are similar with regard to these characters and 
behave similarly in their inheritance. 
There has been a difference in the inheritance of these characters in different 
years. In 1909-11 the characters in hybrids between, miliaris and HZ. esculentus 
were invariably inherited through the maternal parent, the reciprocal crosses 
being thus unlike. In 1912 H. esculentus 9 x H. miliaris g has been maternal 
as previously, but the reciprocal has been paternal. The maternal inheritance 
has thus changed into a dominance of Z. esculentus over LZ. miliaris. 
While in former years there was no exception to the rule given, in 1912 several 
cultures have shown a difference. One fertilisation gave larvee, some paternal, 
others maternal, for both characters. In several cases the hybrids have ‘all in- 
herited the absence of green pigment from one parent, while some of the larvze 
have had both, some one and some neither posterior epaulettes. The last-men- 
tioned shows that the characters may be inherited independently of one another, 
the absence of green pigment coming from HW. esculentus and the absence of 
epaulettes from #. miliaris. 
No parallel seems to be known to this reversal of inheritance. The cause is 
unknown, but it is suggested that it is due to a condition of the parents, and not 
to the environment of the larvae : because (1) one of the pure forms has been much 
more diflicult to raise this year than in previous years; (2) different cultures from 
the same fertilisation always showed the same inheritance; (3) it has been im- 
possible to alter the inheritance artificially. 
In the past summer large numbers of pure-bred and hybrid Eehini have been 
raised through metamorphosis. The inheritance of a tube-foot character has been 
investigated, but it has been found to be too variable to give definite results. It 
is hoped that a second generation of the hybrids will be obtained. Some are 
already large and old enough to be mature. 
5. On Methods of raising Parthenogenetic Lurve of Hehinus 
esculentus. By Dorotuy Jorpan Luoyp, B.Sc. 
This work was carried out in conjunction with Dr. Cresswell Shearer during 
the seasons 1911 and 1912 at the laboratory of the Marine Biological Association, 
Plymouth. The experiments were made in order to obtain a method that could 
be applied to the sea-urchins of the English coast, and in the hope of raising some 
of the parthenogenetic larvee to maturity. We have been successful in rearing 
the plutei through the late stages, and large numbers in our cultures formed 
Echinus-rudiments. A few of the larve completed their metamorphosis, but we 
on not succeeded in getting the young urchins to live for more than a few 
ays. 
The methods used were those elaborated by Loeb and by Delage, and a new 
method which combines certain features from each of these. Loeb’s method 
consists in treating the unfertilised eggs with butyric acid to cause mem- 
brane formation, and subsequently with hypertonic sea-water. Owing to the 
condition of the sea-water at Plymouth it is necessary after membrane formation 
to place the eggs in water of raised OH-ion concentration before treating them 
with hypertonic sea-water. The modification of Loeb’s method which we em- 
ployed is as follows. The unfertilised eggs were placed in :— 
(1) 3 c.c. N/10 butyric acid+-50 c.c. sea-water for 1:5 minutes. 
(2) O'2c.c. N/10 NaOH + 50 c.c. sea-water for 6 minutes. 
(3) 8 c.c. 2°5 M/NaCl+5 c.c. sea-water for *75—1 hour. 
The best experiments with this method gave 60 per cent. blastulee. The larvie 
were healthy and grew well. 
