ARTIFICIAL PARTHENOGENESIS IN ECHINUS ESCULENTUS. 523 
On Methods of Producing Artificial Partheno- 
genesis in Echinus esculentus and the 
Rearing of the Parthenogenetic plutei through 
Metamorphosis. 
By 
Cress well Shearer, 
University Lecturer in Experimental Morphology, Cambridge, 
and 
Dorothy Jordan L,loyd, 
Batluu'st Student, Newnham College, Cambridge. 
With Plates 31) to 32. 
Contents. 
II. 
IV. 
Introduction .... 
PAGE 
. 523 
Loeb's MgCl; Method and Delage'.s HCl Method . 
. 5.32 
Loeb’s Improved Metliod 
.533 
Deluge's Method .... 
. 538 
Combined Method .... 
. 543 
Conclusion and Summary 
. 545 
I. IXTKODUCTION. 
Dcking the last seven or eight years extensive experiments 
have been carried on in the laboratory of the Marine Bio- 
logical Association in rearing various marine larvae. In 
particular, attention has been directed to perfecting means 
for bringing the delicate plutei of Ecbinoderms through 
metamorphosis. As the result of considerable investigation 
a method has been found by which these larvae can be reared 
with considerable ease and certainty. We have already 
successfully raised at Plymouth several species of sea-urchins 
and their hybrid crosses to the adult condition. 
This suggested to us that these methods might equally be 
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