288 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of position — within the vessels, in association with the endothelium — 
point to the conclusion that all these structures in Enchytraeidse arc 
moiqohologically alike. What their functional import is remains obscure. 
Eyes of Hirudinea.* — Dr. R. Hesse describes the optic organs in 
about a dozen species of Hirudinea. He begins with the Gnatlio- 
bdellidae, where the eye-structure is simplest, and discusses Piscicola , 
Branchellion , Pontobdella , Clejpsine, &c. Among Ehynchobdellkke he 
describes Nephelis , Hirudo, &c. In many cases his descriptions are 
only supplementary to previous work by others. 
The optic cells form the structural basis ; they occur diffusely, or in 
stretches, or in close aggregates. They differ, of course, in detail, but 
they are all alike in being continued into a nerve-fibre, and in having 
vacuolar structures in their plasma. These vacuoles are the specific 
characteristics of# the optic cells, analogous to rods and cones. The 
pigment accumulations associated with tho optic cells are, as usual, 
“ Blendungsv or richt ungen .” 
In all Hirudinea, even in those without eyes, there are scattered 
optic cells ; in Clejpsine bioculata and Cl. sexoculata the number of free 
cells decreases as the eyes increase ; in Ichthyobdellidse only Piscicola 
has true eyes, in Pontobdella there are scattered optic cells, while 
Branchellion is between the two states. These and similar facts point 
to the conclusion that the eyes of Hirudinea have arisen by aggregation 
of optic cells, and by the closer association of these with pigment accu- 
mulations. 
Rotatoria. 
Some new Forms of American Rotifera.j — Dr. A. C. Stokes gives 
a description, with plate, of the following six “ presumably ” new species 
of Rotifers : — Proales hyalina , Notommata vorax, Biglena contorta, Mas - 
tigocerca sjpinifera , Cathy jpna scutaria , and Cathy pna glandulosa. The 
first-named, P. hyalina , is certainly Ehrenberg’s Notommata tuba , which 
Mr. C. Rousselet has recently described and renamed Cyrtonia tuba.% 
N. vorax seems to have considerable resemblance to Dujardin’s N. torulosa 
with its globular auricles, if it is not identical with it. Diglena contorta 
seems to have much in common with Ehrenberg’s N. forcipata , and, as it 
Das no eyes and possesses auricles, it is questionable if it be a Biglena. 
Dr. Stokes gives this form two dorsal antennm, which is a very unusual 
feature. 
Lacinularia elongata. a new Rotifer.§ — Mr. T. Shephard, in de- 
scribing this new Lacinularia , gives the following principal charac- 
ters : — Clusters fixed, with a dense matrix of adherent tubes of dirty brown 
colour ; body of individual narrow and much elongated ; corona only 
little wider than the body, slightly oval. A plate of five figures accom- 
panies the description. 
Brachionus bakeri and its Varieties.! — Mr. C. F. Rousselet’s object 
in figuring all the principal varieties of this Rotifer has evidently been 
* Zeitschr. f. wiss. Zool., lxii. (1897) pp. 671-707 (2 pis.). 
f Ann. and Mag. Nat. Hist , June 1897, pp. 628-33 (1 pi.). 
X Of. this Journal, 1895, p. 317. 
§ Victorian Naturalist, May 1896 (1 pi.). 
II Journ. Quekett Micr. Club, vi. (1897) pp. 328-32 (1 pi.). 
