994 SUMMARY OF CURRENT RESEARCHES RELATING TO 



by several observers. Dabl also pointed out that Micrommata virescens 

 and M. ornata are dimorphic varieties of the same species ; the fact 

 that both species are sexually mature at the same time, and that 

 specimens of each, the same age in both species, have been found at 

 the same time at once negatives this view. 



Dr. F. Karsch calls attention * to the writings of 0. Herman, who 

 has stated, and has priority in the statement, that Meta segmentata 

 has two generations ; other species are mentioned by the same writer 

 whicb have two generations, without, however, exhibiting a marked 

 seasonal dimorphism ; some of them are Epeira umhratica, Gyrtophora 

 cornea, Tetragnatha extensa. Micrommata ornata is, on the contrary, 

 stated by Herman to be undoubtedly the young male of M. virescens. 



Australian Pycnogonida.t — Mr. W. A. Haswell describes one 

 new genus (Nympliopsis) and eight new species of Australian Pycno- 

 gonida, bringing up the list to eighteen species. 



6. Crustacea. 



Alimentary Canal of Crnstacea.+ — Herr J. Frenzel reviews in a 

 lengthy memoir the histological structure of the alimentary canal of 

 Crustacea, and especially of the mid- and hind-gut, which have not 

 yet been studied in such detail as the other portions. He discusses 

 the general anatomy of the tract, noting the extreme shortness of the 

 mid-gut with its two associated glands, the large double liver with 

 two ducts, and the much smaller variously-shaped diverticula, which 

 open somewhat dorsally just where the hind-gut begins. A section 

 of the hind-gut reveals a number (six or so) of thick bands, which 

 run spirally within, narrowing the lumen of the gut. A cross section 

 of the hind-gut exhibits from within outwards (1) a chitinous cuticle, 

 (2) the epithelial layer of the matrix or hypodermis, with cylindrical 

 cells, (3) interspersed sinewy strands, probably of connective tissue 

 origin, and in association with (4) muscle-bands, some of which run 

 obliquely, and are not therefore seen continuously in a single section, 

 while others sometimes occur running longitudinally ; (5) glandular 

 structures ; (6) abundant fibro-cellular connective tissue, usually with 

 lacunae containing blood ; (7) a sheath of circular muscles ; and (8) an 

 external layer of connective tissue, firmer and more fibrous than the 

 internal one, and penetrated by vessels which supply the lacuusB of 

 the former. 



The ridges do not extend into the mid-gut, though the transition 

 is not abrupt. A cross section of the mid-gut exhibits (1) the 

 cylindrical epithelium, of endodermic origin, with a covering of small 

 bristles ; (2) a thick, strongly refracting, double-contoured mem- 

 brane, tbe basement membrane, or tunica propria; (3) a circular 

 muscle-sheath of several layers, not well developed, or even absent 

 on the appendages of the mid-gut; (4) a connective tissue layer, 

 sometimes exclusively fibrous. The details of the complicated passage 



* Zool. Anzeig., viii. (1885) pp. 532-3. 



t Proc. Linn. Soo. N. S. Wales, ix. (1885) pp. 1021-34 (4 pis.). 



1 Arch. f. Mikr. Anat., xxv. (1885) pp. 137-90 (2 pis.). 



