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POPULAR SCIENCE REVIEW. 
ambulacra running from the mouth to the vent, which are placed 
centrally at the two poles of the test, Professor Wyville Thom- 
son only cites two species, and as these belong to the family 
Cidaridse, in which the development, so far as is known, always 
takes place without the intervention of any so-called 44 pluteus- 
stage,” the chief interest attaching to these forms consists in the 
nursing habits of the mother. No example of this kind had 
previously been observed. 
One of the two species in question, a true Cidaris , nearly 
allied to the common G. vapillata of northern seas, was dredged 
about the middle of January at depths of from 50 to 70 fathoms 
in Balfour Bay, a recess near the head of Boyal Sound, in 
Kerguelen’s Land. The eggs of this Urchin, after escaping 
from the apertures in the genital plates at the summit of the 
test are passed down along the surface of the test towards the 
mouth, where they are received in a kind of open tent formed by 
the bending inwards over the mouth of the smaller, slightly 
spathulate primary spines which are articulated to about the 
first three rows of tubercles surrounding the peristome. Here 
the eggs are retained, and the young, which are directly developed 
from them, are kept under shelter until they have attained a 
diameter of about T x ¥ inch, when they are entirely covered with 
calcareous plates, and furnished witli spines exceeding in length 
the diameter of the test. It is true that even before this size is 
reached some of them are seized with a spirit of wandering, and 
may be seen 44 straying away beyond the limits of the ‘nursery,’ 
and creeping with the aid of their first five pairs of tentacular 
feet, out upon the long spines of their mother,” but a short 
excursion seems to satisfy them, and the little truants soon 
return to the protection of their tent. From its nursing habits 
Sir Wyville Thomson names this species provisionally Cidaris 
nutrix. 
The other nursing Cidarid here described is a species of the 
genus Goniocidaris , which differs from Cidaris properly so- 
called chiefly by the presence of a zigzag impressed line running 
down the middle of each ambulacral and interambulacral area. 
The genus includes but few species, mostly confined to the 
cooler parts of the Southern Ocean, and the one now under con- 
sideration, identified by Sir Wyville Thomson with the Gonio- 
cidaris canaliculata of A. Agassiz, was dredged in January off 
Cape Pembroke, East Falkland Island, in about 10 fathoms of 
water. The arrangement for the protection of the eggs and 
young in this animal is on the same principle as in the Cidaris 
just noticed, but with this difference that the nursery is placed 
at the opposite pole of the test. The summit of the test 
exhibits a flat space, including not only the apical plates, but 
at least the first pair of plates belonging to each interambu- 
