ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
175 
genital area. The porous cliitinous carapace of Arrenurus is only 
gradually developed after the final eedysis. The appendage of the body 
of the immature male of the same genus is in a rudimentary condition 
after the last eedysis. All eight-footed iVesasct-larvas have four genital 
acetabula, which are arranged by pairs. 
Unrecorded British Parasitic Acari.^ — Mr. A. D. Michael describes 
three species of parasitic Acari which appear to be new: — Myocoptes 
tenax, from the field-vole (^Arvicola agresfis), is the second member of its 
genus ; both species live on rodents among the hairs, to which the 
females of the new species cling so tenaciously that the grasp is often 
not relaxed even in death. Symbiotes tripilis is parasitic on the hedge- 
hog, along and between the quills of which it runs up and down with 
great rapidity ; unfortunately, the male of this species has not yet been 
discovered. The third form is the representative of a new genus — 
Goniomerus muscuUnus — which it is very difficult to define accurately, as 
the present form is so extremely minute ; it was found on the surface of, 
or very slightly buried in a depression of the skin lining the inner side 
of the external ear of the short-tailed field-vole (Arvicola agrestis). The 
author gives detailed accounts of these three new forms. 
Types of Metamorphosis in Development of Crustacea.| — Mr. I. 
C. Thompson made this the subject of his last (1890) address to the 
Liverpool Microscopical Society ; as he well remarks, the student of 
minute pelagic forms often meets with immature forms, many of which 
are crustacean larvm, and their study is by no means easy. 
Brachyura and Anomura.J — Sig. Gr. Cano describes the crustaceans 
of these orders collected on the “ Vettor Pisani ” ex]3edition. The list 
includes a dozen new species, and two new genera — Podohuenia in the 
family Periceridm, and Euryetisus in the family Cancridae. 
Excretory Organs of Gammarus.§— Sig. A. Della Yalle having 
sprinkled carmine powder on the water tenanted by young forms of 
Gammarus pulex, found after several days that the pigment-granules had 
accumulated within the animals in the antennary gland, and at the 
bases of the maxillary, thoracic, and abdominal appendages. The 
granules in the antennary gland were very numerous, minute, and 
altered in colour ; those at the b^ses of the aj)pendages remained bright 
red. His experiments, though not sufficiently extended, suggest the 
excretory significance both of the antennary gland, and of those on the 
thorae'e and abdominal appendages. 
Paracopulation in Eggs of Daphnids-H — Prof. A. Weismann and 
Mr. C. Ischikawa formally apply the term of j^aracopulation to the 
processes of which they have already given some account. These 
processes consist essentially in the presence in the egg of a cell other 
than the sperm-cell, which at first takes no share in the formation of the 
embryo, but in an early stage of cleavage unites with one of the cleavage- 
cells in such a way that we are compelled to speak of copulation of the 
* Jouru, Linn. Soc., xx. (18S9) pp. 400-6 (1 pi.). 
t Liverpool, n.d., 8vo, 19 pp. ; reprint from ‘ Kesearch,’ Feb. 1890. 
X Boll. Soc. Nat. Napoli, iii. (1889) pp. 169-268 (1 pi.). § T. c., pp. 269-72, 
11 Zool. Jahrb., iv. (1889) pp. 155-96 (7 pis.). 
