328 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
trochophore type ; it is characterized by more or less numerous rings of 
cilia, one of which (the oral corona) is placed at the level of the mouth, 
and is remarkable by its persistence ; by a mesoderm derived from a 
small number of initial cells (often two), and by a schizocoelic coelom ; 
the Brachiopoda alone form an exception to this rule ; and by a pair of 
excretory organs or cephalic nephridia which appear very early in the 
course of development. 
The first subdivision is that of the Polymeria ; in them the meso- 
dermal stripes early give rise to dissepiments which divide the coelom 
into segments. The first series is that of the P. Intacta or Annelids, 
among which we have the Archiannelids, achsetous Euannelids, repre- 
sented by the Hirudinea, and the Chsetopodous Euannelids. The 
P. distincta or Pseudannelids are represented by the Sternaspidia and 
Gephyrea. The second subdvision is that of the Monomeria, in which 
there is a simple coelom, or one divided into sinuses. Here we have the 
Rhyncota or unarmed Gephyrea, the Brachiata or tubicolous Gephyrea, 
of which Phoronis is a type, the Bryozoa, the Brachiopoda, the Yelata — 
or our old friends the Rotifers, the Amphineura, and the Mollusca ; 
of these last the Solenoconcha form the subtype of Premollusca, while 
Lamellibranchs, Gastropods, Pteropods, and Cephalopods unite to form 
the Eumollusca or true Mollusca. It is not for us to apologize for the 
numerous hybrid names proposed in this memoir. 
Abnormalities in Crayfish and Earthworm.* — Dr. W. B. Benham 
reports an observation on a Crayfish in which, with normal ovary, there 
were two oviducts on either side, one of which opened on the 11th and 
the other on the 13th appendage ; there were no indications of herma- 
phroditism. This, in conjunction with other facts, points to the pos- 
sibility of a pore and a duct for each of the last three ambulatory 
appendages. It is possible that Arthropods had originally a pair of 
nephridia in each segment; in the Crustacea most of these are sup- 
pressed, but those of the second antennary segment and of the second 
maxillary remain, and with these three would help to fill up the series. 
Of several thousands of common earthworms examined by Dr. Benham 
only one case of asymmetry has been observed. In this the genital 
orifices of the right side were on the 13th and 14th segments, instead 
of on the 14th and 15th as on the left side and in normal earthworms. 
On the right side there was only one spermatheca and two sperm-sacs, 
while the ovary was in segment xii. instead of xiii. ; the calciferous gland 
was also absent from the right side of segment xii. 
Mollusca. 
Census of Scottish Land and Freshwater Mollusca.f — Mr. W. D. 
Roebuck summarizes the records of Land and Freshwater Mollusca 
which have so far been authenticated from Scotland ; these records are 
comparatively small. In all 103 species are registered. This list 
should be very useful to Scottish naturalists. 
* Ann. and Mag. Nat. Hist., vii. (1891) pp. 25o-8 (1 pi.), 
f Proc. Roy. Phys. Soc. Edinb., 1889-90 (1891) pp. 437-503. 
