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SUMMARY OF CURRENT RESEARCHES RELATING TO 
of pleopods, and these, for some time before oviposition, are filled with a 
milky-white substance. On the removal of the cuticle from a pleopod 
the tissue is seen to be studded with very minute round bodies, which 
are the cement-glands. In section the gland is composed of a very 
delicate sheath of connective tissue, and a simple epithelium formed of 
tall, pyramidal cells. The apices of the cells meet near the centre of 
the gland, the opening of which to the exterior it is impossible to detect. 
Shortly after oviposition the glands may be seen to have undergone a 
remarkable change in structure. They are enlarged and the epithelial 
cells appear to be degenerated, while the cell-outlines are very dim. 
Protective Adaptations in Crabs.* — Dr. V. Haecker discusses, in an 
interesting essay, “ the specific variation of Arthropods,” with especial 
reference to the protective adaptations exhibited by crabs. He begins 
by noticing that certain lines of variation are characteristic of certain 
orders and families ; thus sexual dimorphism is marvellously varied 
among Lamellicorns, but restricted among Caraboidea, these being 
notable for their protective coloration. So the Copepods are manifold 
in their sexual dimorphism, while the Decapoda are restricted as to this, 
but are notable for their protective adaptation. Rapid movement, 
burrowing, and masking illustrate their protective instincts. Some 
cases of masking have been recently studied with much care by Aurivil- 
lius. That the masking of Hyas, Dromia , &c., is an active process 
is beyond doubt. It has been repeatedly observed. On Dromia , the 
author found peculiar hooked hairs (noted by Aurivillius on Hyas), 
which make the fixing of foreign objects easier. But these are 
restricted in Dromia to the anterior end of the carapace and to the upper 
surface of the anterior limbs, for the posterior limbs in the Dromia - type 
have been modified so as to hold large objects on the crab’s back. It is 
suggested that in the history of the Dromia-type, two modes of masking — 
by means of hooked setae and by means of backward- turned appendages 
— have predominated at different epochs. 
Limnoria lignorum.j — The commission appointed by the Royal 
Academy of Amsterdam to investigate the life and work of Limnoria 
lignorum has given in an elaborate report. The animal’s geographical 
distribution, structure, and habits are discussed at length, but due 
attention has been given to its occurrence on the Dutch coast, the 
damage which it does, and the possibilities of lessening the evil. 
Parthenogenetic Ova of Artemia salina.J — Dr. A. Brauer finds that 
the directive spindle in these ova consists not of 24-26 bipartite chromo- 
somata, but of 84 tetrapartite elements, which are arranged not in one 
ring nor in two, but in a round plate. This runs counter to the results 
of Weismann and Yom Rath. 
The maturation occurs in two ways. Only one polar body may be 
extruded, the remainder becoming the final ovum-nucleus. Or, a second 
division may occur, but without extrusion, the retained half uniting its 
chromosomata with those of the ovum-nucleus in the first segmentation- 
spindle, behaving, in fact, as if it were a sperm-nucleus. In the first 
* Ber. Nat. Gesell. Freiburg i. B., vi. (1891) pp. 90-100. 
+ Verh. K. Akad. Wet. Amstel., 1893, vi., 103, and xcvi. pp., 7 pis. 
X Zool. Anzeig., xvi. (1893) pp. 138-40. 
