342 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
more closely allied than some later systematists have been inclined to 
allow. The mode of formation of the endoderm by a process of multi- 
polar delamination is only seen in these two groups ; the mode of origin 
of the stomodaeum is the same in both, and the early formation of the 
body-cavity in the legs of Spiders has an exact parallel in Pallene and 
Phoxichilidium. In both groups, again, there are well-marked diverticula 
from the mid-gut into the legs, and in both the first pair of appendages 
is chelate. 
There is a general resemblance between the Nauplius of the Crustacea 
and the larva of Pycnogonids, but the differences become greater and 
greater the more closely we examine the two forms ; for example, none 
of the appendages of the Pantopod-larva are biramous, and the first pair 
is chelate. As to the affinities to the trochophore-larva, the author 
suggests that the Arachnids may have come from Annelid ancestors with 
many segments, and that the pantopod represents the most anterior 
segments of the adult Sea-Spiders, and, therefore, to some extent the 
anterior segments of Annelids or of the trochophore. But at no time in 
the ontogeny of the Pycnogonids have the trochophore and pantopod 
larvas been transformed the one into the other, as Dohrn believes. 
Mr. Morgan next gives a detailed account of the remarkable meta- 
morphoses of TanystyJum which can hardly be made intelligible without 
figures. 
In the third section of the paper the structure and development of 
the eyes of Pycnogonids are considered. All the evidence seems to show 
that the eye has developed by the turning in of two sides of a primitive 
optic vesicle, and that the simple eyes of Insects furnish all the inter- 
mediate stages, both in development and in adult structure, between a 
simple cup-like invagination and the three-layered condition of the 
Pycnogonid eye. 
The development of this eye seems to have been abbreviated, and 
this shortening of the history complicates the matter ; the presence of the 
eye in all the larval stages, in which it was presumably functional, must 
have changed to a very great extent the original process. Yet in all 
stages the three-layered condition of the eye may be recognized. The 
author thinks that in Pycnogonids the invagination (of the Arachnid 
type) has been retarded, so that, one end of the invagination having been 
formed, the inturned and inverted cells have functioned as larval eyes, 
and as the animal increased in size the invagination kept pace, adding 
more and more cells to the layers of the eye, so that all of the stages 
had presumably functional eyes, and at the same time the larva retained 
the original type of Arachnid invagination. 
e. Crustacea. 
Bathynectes, a British Genus.* — Canon A. M. Norman reports that 
Bcithynectes, a genus formed by Stimpson for certain Crabs nearly related 
to Portunns, is represented by two species in the British area; one, 
B. siiperba, has only been taken twice from 345 to 400 fathoms, but 
B. longipes appears to be much more common. 
Ann. and Mag. Nat. Hist., vii. (1891) pp. 274-0. 
