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E. W. MACBRIDE. 
pluteus was formed, and then a certain number were 
transferred to an eight-gallon jar fitted with a plunger 
containing similar sterilised sea-water to which a mixture of 
Nitschia and Pleurococcus cultures was added. This jar was 
also covered in, and the cover as well as three fourths of the 
periphery were sheathed in black paper in order to protect 
the larvae from the baneful effects of too much light. In this 
jar the abnormal larva first to be described was found, and in 
the same jar a week or two later thirty or forty fully 
metamorphosed echini were found creeping about. To the 
best of my knowledge this is the first time that the eggs of 
a sea-urchin have been reared through the whole of their 
development until the completion of the metamorphosis in an 
inland laboratory. 1 It is to be noted that whilst the sea- 
urchins came from Plymouth, on the English Channel, the sea- 
water came from Lowestoft, on the North Sea. The water was 
purified by shaking it with animal charcoal, which was 
allowed to settle; then the supernatant liquid was decanted 
off and passed under pressure through a Berkfeld filter. In 
this way the water was cleansed from all bacteria, and also 
from all soluble organic toxins, and when in this purified 
condition it received the culture of diatoms which is to 
serve as food for the larvae. 
It will be noted that the method employed for rearing the 
larvae is a combination of the one used by me in Plymouth 
in 1898 and 1899 (5), and the one recommended by Dr. 
Allen (1) ; I take this opportunity of expressing my in- 
debtedness to Dr. Allen for his assistance and advice in the 
matter of fitting up the salt-water aquaria in the Imperial 
College. 
Dr. Allen keeps the larvae in the half-gallon jars until they 
1 Since wilting this sentence I have learned, through a letter of Prof. 
Stanley Gardiner to ‘Nature’ (July 27tli, 1911), that a single hybrid 
between the species Echinus miliaris and Echinus esculentus 
had been reared through its entire development in the Zoological 
Laboratory of the University of Cambridge a week or two before my 
specimens had completed their development. 
