948 SUMMARY OF CURRENT RESEARCHES RELATING TO 



abundantly observed, the ciliated areas or grooves are less definite, 

 and the colour of the affected area is turbid and slightly yellow. Tbo 

 mucous cells exhibit marked modifications, e.g. a marked abundance 

 of disproportionately large granules, and a longer, narrower shapo. 

 In the ciliated cells, tho cilia disappear, or become fused together, or 

 become, less frequently, markedly smaller, as Drasch * has already 

 noted. The epithelium generally is much less conspicuous, and tho 

 ciliated grooves much flatter. The investigation, which cannot yet 

 be regarded as complete, was extended to other amphibians, and to 

 the rabbit. 



Direct Communication of the Blood with, the surrounding 

 Medium. | — Hcrren C. F. and P. B. Sarasin describe the tubules of 

 communication in Epicrium glutinosum, by means of which the con- 

 tents of the blood capillaries communicate with the intercellular 

 spaces and so with the outer world. Among the Mollusca they 

 examined a Planorbis and a Paludomus ; they found gland-ducts of 

 about tho diameter of an epithelial cell and tubules with a diameter 

 one-tenth or one-twelfth of this, which end freely in the subepithelial 

 tissue which, as wo know, is filled with blood. These tubes appear 

 to subserve respiration, and cannot allow of the sudden entrance of a 

 quantity of water. Among the Oligochaita two species of Perichseta 

 were found to have considerable intercellular spaces between the 

 cells of the epidermis, and these are free on the side of the cuticle, 

 which is traversed by a number of pores, the larger of which corre- 

 spond to the glandular cells. Numerous blood-vessels pass into the 

 epidermis. In the land-leech of Ceylon very similar structural 

 relations were observed. The authors think that these undoubted 

 cases of communication between the blood and the surrounding 

 medium are all of advantage in the process of respiration. 



y. General. J 



External Markings.§— Prof. T. Eimer, in resuming his well- 

 known opinions in regard to the external markings of mammals, 

 molluscs, butterflies, ivc, lays stress on the origin of species from 

 constitutional causes, without any primary relation to utility. 



Methods of Defence in Organisms. || — Mr. C. Morris adds some 

 remarks to his previously published paper on this subject,^ in which 

 he especially treats of the sponge from the point of view of defence. 

 Of all animal types this is the one which is the least protected by 

 defensive appliances ; what adaptation there is appears to reside in the 

 peculiar system of inhalent and exhalent apertures, for the currents 

 enter only at minute apertures, and close up completely when not in 



* SB. K. Akad. Wiss. Wien, Ixxx. (1870), and lxxxii. (1881). 



t Arbeit. Zool. Zoot. Inst. Wiirzburg, viii. (1886) pp. 94-101. 



X This section is limited to papers which, while relating to Vertebrata, 

 have a direct or indirect bearing on Invertebrata also. 



§ Biolog. Centralbl., vi. (1886) pp. 285-6. (Bericht Versamrnl. Dentsch. 

 Naturf. Stiassburg, 1885). 



|| Proc. Acad. Nat. Sci. Philad., 18S6, pp. 25-9. t A >^% P- 214. 



