176 SUMMARY OF CURRENT RESEARCHES RELATING TO 
entiated, and the sac closes completely. It would seem that the general 
cavity of the adult was primitively a simple excretory canal. The author 
throws doubt on the correctness of the homology between the larval 
kidney of Cirripedes and the test-gland of other Crustacea. 
Revision of the Cladocera.* — M. J. Richard has prepared what 
would appear to be the first part of a revision of the Cladocera, were it not 
that the second half has not appeared in the succeeding number of the 
‘ Annales.’ The author gives a full, if not exhaustive, bibliography of 
his subject by reciting 429 titles. He gives a general account of, and 
revises the species belonging to the Ctenopoda. 
Annulata. 
7 Hew Classification of Polychseta.t — Dr. W. B. Benham makes 
some suggestions for a new and, we may add, much needed classification 
of this group. He thinks they may be divided into two grades : (1) 
Eucephala, in which the prostomium retains its original condition as a 
lobe overhanging the mouth, and the peristomium shows no tendency to 
overgrow it ; the body segments are all alike. The second grade may 
be called that of the Cryptocephala, as the peristomium grows forward 
and fuses or even entirely conceals the prostomium, which is greatly 
reduced. The body segments are differentiated into two groups indicated 
by the sudden alteration of the chaetae, and internally by certain differ- 
ences. The Eucephala include four sub-orders : — 
(1) Nereidiformia ( = Errantia auct. together with Ariciidae). 
Here the prostomium generally carries tentacles and palps and the 
peristomium usually carries special cirri. There is a pharynx which is 
frequently armed with jaws. 
(2) Scoleciformia including the four families, Opheliidae, Arenicolidae, 
Scalibregmidae, and Maldanidae. There are no prostomial tentacles 
or palps, and the peristomium is without special cirri. There are no 
jaws, - though the anterior end of the gut may be eversible. 
(3) Terebelliformia (Cirratulidae, ChlorhaBmhhe, Sternaspidae, Tere- 
bellidae, &c.). The prostomium carries tentacular appendages, the 
achaetous peristomium may carry filamentous processes ; buccal regions 
not eversible. 
(4) Capitelliformia includes the family Capitellidae. 
The second grade is divided into two sub-orders : — 
(1) Spioniformia (Spionidae, Magelonidae, Chaetopteridae, Ammocha- 
ridaa) ; they retain the prostomium as a small lobe without definite ten- 
tacles or palps, but the peristomium is relatively large, and extends 
forwards on either side of the prostomium. This segment usually 
carries very long flexible tentacles ; buccal regions eversible, but with- 
out jaws. 
(2) Sabelliformia (Sabellidae, Eriographidae, Serpulidae, Hermellidae). 
The prostomium is in most cases entirely concealed by the great deve- 
lopment of the peristomium, and may be reduced to mere sensory knobs, 
but the palps are very greatly developed and function as gills. 
* Ann. Sci. Nat., xviii. (1894) pp. 279-389 (2 pis.), 
t Rep. Brit. Assoc., 1894, pp. 698-7. 
