46 SUMMARY OF CURRENT RESEARCHES RELA TING TO 



e. Crustacea. 



Glands of Alimentary Canal in Decapoda.* — Dr. Hans Wallengren, 

 by the use of nitrate of silver, has been successful in making a number 

 of preparations of the alimentary canal in Decapod Crustacea, which 

 show clearly the glands called intestinal by various authors. He finds 

 that these occur freely in the wall of the oesophagus, as well as on such 

 outgrowths of the mouth region as upper lip and labium, and also on 

 the wall of the hind-gut. The function of the glands remains un- 

 certain. Perhaps those of the oesophagus are salivary, and those of the 

 hind-gut, mucous glands, but all may be mucous glands. 



Colours of American Crayfish. j — W. J. Kent finds that in Cambarus 

 hnmunis, and some other species, the colours generally resemble those of 

 the surroundings, except that the colour of those living in shallow water 

 in small streams is red. This fact, the author believes, is due to the 

 influence of light, which has the power of turning the pigment of the 

 crayfish red. He finds confirmation of this view in the fact that 

 in C. diogenes, which is a burrowing species, the colour is varied in 

 spring, but in autumn, after exposure to the light throughout summer, 

 nearly all the individuals are red. In confinement the crayfish acquire, 

 though slowly, the colour of their surroundings. 



Mysis relicta in Ireland. J — W. F. do Vismes Kane, in an inter- 

 esting paper, reports the abundant occurrence of this species in Lough 

 Neagh and Lough Erne, into which it was doubtless introduced by the 

 Glacial sea. 



Life-History of Monstrillidee.§ — A. Malaquin, in the course of some 

 observations on the reproduction of the Annelids Filograna and Salma- 

 eyna, unexpectedly obtained, instead of the trochospheres for which he 

 hoped, a cloud of Copepoda of the family MonstrillidaB. These emerged 

 from the bodies of the Annelids, and as the life-history has not hitherto 

 been adequately worked out, he gave up his first research and devoted 

 himself to the Copepoda. The results, of which the following are the 

 most striking, are published in an extensive memoir. From the eggs 

 contained in the ovigerous sacs of the free-swimming female, nauplii 

 develop, which possess the normal number of appendages. Of these, 

 the first have the usual structure, the second are slightly modified, while 

 the third pair (mandibles) are entirely converted into organs of fixation. 

 There is no alimentary canal, but the eye is present and well developed. 

 There is a distinct nerve-mass, and the muscles arc striated. These 

 nauplii attach themselves to their host by means of their piercing 

 mandibles, and lose their cuticle, appendages, and furcal bristles, while 

 the central mass of cells only penetrates first the skin, and then one of 

 the blood-vessels of the host. During this period of penetration, the 

 only differentiated part of the body is the nauplius eye, which is re- 

 tained, but even this gradually breaks down, so that the Copepod within 

 the blood-vessel has returned to an undiil'erentiated embryonic condition 



* Zeitschr. wiss. Zool., Ixx. (1901) pp. 321-45 (12 figs.). 



f Amer. Nat., xxxv. (1901) pp. 933-6. 



X Ami. Nat. Hist., viii. (1901) pp. 391-7. 



§ Arch. Zool. Exper., ix. (1901) pp. Sl-232 (7 pis. and 6 figs.). 



