4 Bch, 
EOHINODERMATA. 
? larva) occurred, while PluteV' and Bipinnaric&*^ were constantly 
taken in the towing-net in the warm and temperate seas. 
According to Studer (19), the arms oi Lahidiaster are thrown off suc- 
cessively, swollen with mature ova, for the purpose of propagation 
(^Cf. Sars’s similar suggestion on Brisinga ; Zool. Rec. xii. p. 653). 
Giard describes Echinocardium cordatum as living buried in the sand at 
the depth of 15-20 centimetres, in a cavity lined with a glutinous secre- 
tion ; two tubes of the thickness of a quill communicate with the surface, 
one of them terminating at the central point of the ambulacral star, the 
other at the anal aperture ; the water penetrates by the first-named tube, 
which contains the long suckers of the anterior ambulacrum, the move- 
ments of which convey the alimentary particles to the mouth ; the anal 
tube serves for the escape of the sand which has traversed the digestive 
system (0. R. Ixxxii. pp. 76 & 77 ; Ann. N. H. 4, xvii. pp. 261 & 262). 
According to Selenka’s observations (16), each of the eight large tenta- 
cula of Cucumaria {doliolum) are successively withdrawn and reflected into 
the mouth, to be cleared of the adherent or captured animalcules, and 
the two small ventral tentacles are employed during the subsequent pro- 
trusion of the large one as a sort of comb for stripping them completely 
of their whole catch. . The fecundation of the ova probably takes place 
in the atrium of the mouth, as the females begin to agitate their tentacles 
violently each time the males eject their clouds of spermatozoa into the 
water. Carpenter (4) has ascertained that the food of Crinoids con- 
sists of minute Entomostracay Diatoms, spores of Algce, Feridinium, &c. 
Evolution. — Some data as to the evolution of the species, which in their 
young state are nursed by their parents, as stated above, are given in the 
papers of C. W. Thomson (22b) and Agassiz (2). The approximation of 
the young Hemiaster to the type of the regular Echini — mouth nearly 
central, bivium and trivium completely separated abactinally, vent sub- 
central inside the fasciole — is especially remarkable. 
The embryonal evolution of Jlolothuria and Cucumaria have been 
studied by Selenka (16). Of the fourteen heads under which the author 
embodies the results of his beautiful investigations, the following may 
here be cited : — The eccentric position of the new nucleus, formed in the 
egg after fecundation, determines the position ofi the actinal and abactinal 
pole ; the blastula ” is composed of a single layer of ciliated cells ; it is 
transformed into a “ gastrula ” through the invagination of the vent at 
the abactinal pole, at a place where internally some of the blastodermal 
(endodermal) cells are freed from their connections, and build up a 
‘•mesodermal germ,” from which the amoeboid migrating cells are de- 
veloped, which successively constitute the subcutaneous muscular system, 
the muscular investment of the intestine, and probably also many other 
internal organs. Before the invaginated primitive intestine is made con- 
fluent with the actinally invaginated oral atrium, it has given off a 
diverticulum, which afterwards subdivides in two cavities ; from one of 
which the aquiferous system takes its origin, with the vesicles for the 
tentacula, the ambulacral vessels, organ of Poli, the stone-canal with its 
dorsal pore, etc. ; the other is the first beginning of the largo peritoneal 
cavity, which subsequently pushes aside the primitive body cavity or 
