194 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tarsal nails and of the femoral armatures been independently acquired 

 by these New World and Old World genera, or are they inheritances 

 from a common ancestor ? Of the physiological significance of these 

 structures we know absolutely nothing." 



Commensalism of Termites and Fungi.* — Herr C. Holtermann has 

 found a new illustration of this phenomenon in Java. The walls of 

 the chambers of the underground termite-nests are clothed with the 

 mycele of a fungus, forming heads in which oidia are developed, which 

 form a large part of the food of the termites. When cultivated inde- 

 pendently the termite-nests give rise to an agaric belonging to the 

 subgenus Pluteus, which, however, was not identified with the above- 

 named fungus. 



Stigmata of Rhynchota.f — Herr A. Handlirsch notes the extra- 

 ordinary diversity of the answers given to the question : How many 

 stigmata have the Rhynchota ? He shows that the fundamental type 

 has ten pairs of stigmata, two on the meso- and meta-thorax, and eight 

 on the first eight abdominal segments. The exceptions, especially the 

 reductions in parasitic forms, are discussed. 



Digestion in Cockroach.:): — Herr A. Petrunkewitsch has studied the 

 histology of the alimentary canal, and the physiology of digestion, in 

 Periplaneta orientalis and Ulatta germanica, with special reference to the 

 -crop, and has obtained some novel results. He finds that the intiraa of 

 the crop consists of two layers, of which the outer is distinctly porous, 

 while the inner shows no trace of pores. Nevertheless, the author 

 believes that such pores must exist ; for he finds that, both in the living 

 animal and in the removed intima, oil-drops pass through it, and in the 

 former case can be demonstrated in the epithelial cells. The epithelium 

 •contains three kinds of cell :— (1) polygonal cells with large nucleus and 

 granular cytoplasm ; (2) large polynucleated cells ; and (3) vacuolated 

 cells with 1-3 curved nuclei. These are not independent elements, for 

 (2) and (3) arise from (1), and (2) may again by division give rise to 

 several uninuclear polygonal cells. The crop is interpenetrated by fine 

 tracheal branches, which end either in the lacunar spaces between epi- 

 thelium and muscularis, or actually penetrate the epithelium. In the 

 first case, the tracheal end-cells give off fine protoplasmic processes 

 (tracheal capillaries), which are connected with the fibrillae of the mus- 

 cularis ; in the second case, the end-cell usually insinuates itself between 

 two epithelial cells, from which it can be readily distinguished histo- 

 logically. 



As to physiology, the author finds that the crop is the main organ in 

 which digestion and absorption occur, the mid-gut playing a more in- 

 significant part. Further, he finds that "tracheal digestion" takes 

 place ; in other words, the tracheal end cells directly absorb food from 

 the crop, and transmit this to the tracheal lumina. Within the tracheas 

 it is subjected to a spiral movement, being swept round the grooves of 

 the lining, and is gradually absorbed by the peritracheal cells. Thus the 

 tracheae are in large measure nourished directly from the crop, though 

 they may also in part depend upon the blood. 



* Festsohr. f. Schwendener, 1899, pp. 411-20 (1 fisr.). 



t Verb. Zool.-bot. Ges. Wien, xlix. (1900) pp. 499-510 (2 figs.). 



J Zool. Ja'irb. (Abt. Anat.), xiii. (1899) pp. 171-90 (1 pi.). 



