$: 
1884.] Zoölogy. 305 
hydroid. Cunina has become degenerated by its parasitism or 
commensalism so that the proboscis with young budding from 
it alone remains. Its bell has gone, the mouth opening is no 
longer functional, and the proboscis, which has elongated into a 
stolon attached to the body of a host, is closely crowded with the 
young. The modifications which the same stolon undergoes in 
the Siphonophores, where it is elongated into the axis, and the 
changes which take place in the bell of the primitive Lizzia, by 
which a float or air bubble results, has been sufficiently discussed 
elsewhere. The most widely aberrant forms of development 
among the Siphonophores can be made uniform if we compare 
them with that of the budding Sarsia and Lizzia as the normal 
That exceptional form of development called alternation of 
generation which exists in the fixed hydroids may be regarded 
as the irregular, not the normal, method. It isan adaptation re- 
sulting from peculiar circumstances, and a departure from a rule 
in one direction as that of the Siphonophores is in another. The 
Cunina colonies have resemblances with both fixed hydroids and 
Siphonophores, but have not departed as widely as either from 
the normal method in their older larval and adult conditions.— 
F. W. Fewkes, Cambridge, Dec., 1883. 
A New Peracıc Larva.—While engaged in the study of the 
larvae of our marine Annelids, myattention has been directed to the 
close resemblance which many of them bear to the young of the 
Polyzoa, more especially of the entoproctous genera, Loxosoma, 
and Pedicellina. Several points of resemblance between Actino- 
trocha, the young of a Gephyrean genus called Phoronis, and the 
former of these two polyzoan genera in the adult condition have 
already been suggested by others, while the relationship between 
the young of the Chzetopods, and the larve of Polyzoa have 
been repeatedly commented upon by those who have studied the 
development of both these groups of animals. The larval Che- 
A worm which most closely resembles the young of Loxoso- 
ma is the well-known Mitraria, the comparisons between which 
ve been nowhere more concisely made than by Balfour, in the 
volume of his Comparative Embryology. To prove any 
S*netic relations between these groups, other worm larve, even 
more closely related to the Polyzoa than Mitraria, ought to be 
oa. and it would seem self-evident to every one that 
any intimate connection between the Vermian and Poly- 
roan phyla can be satisfactorily made out, that a larger number of 
on te larval forms of one group or the other should be 
vür Such a larva, which seems to me to fill in part the gap in 
of the larval Annelid and the young Polyzoan, I 
í have taken several times at Newport, and although I am at pres- 
ent ignorant of the adult form which it attains, it seems to me of 
more than ordinary interest as having to a greater extent than 
VOL. xvin, —no. u, 20 
