Aspects of Nature in Southern Peru. 831 



sparent membrane is seen projecting, in the form of a small 

 mamillary process. This is shown at fig. 8, where the egg also 

 exhibits the yolk undergoing segmentation, and two charac- 

 teristic nuclei in the mesial line. When fully mature the ova 

 have a longitudinal diameter of 1 -340th to 1 -320th of an inch. 



Having thus dwelt at considerable length on the intimate 

 structure of Trichocephalus affinis, it only remains for us to offer 

 a few remarks on the present state of our knowledge respecting 

 the development and migrations of this comparatively harmless 

 species. In point of fact, we know little or nothing of the 

 wanderings of this particular worm, but may legitimately 

 infer the occurrence of certain habits from what we observe in 

 the closely allied Trichocephalus dispar. Not long ago Kuchen- 

 meister expressed his opinion, somewhat over confidently, that 

 the little Trichina spiralis found in the muscles of the human 

 body was the young of the last named species ; but a series of 

 beautiful researches by Virchow and Leuckart, carried on in- 

 dependently, have shown that this view is inconsistent with fact. 

 M. Davaine has also recently applied himself to the determina- 

 tion of the development of T. dispar by direct experiment, and 

 he finds that the embryonic formation only takes place within 

 the egg after the ova have been expelled the host, and have 

 been immersed in water for a period of about six months; 

 consequently it may be surmised that either the mature ova or 

 the escaped embrj^os gain access to our bodies in a passive 

 manner when swallowed with the waters we drink. The subject, 

 however, needs further investigation, and the experiments 

 which we ourselves instituted on this score have hitherto only 

 produced negative results. 



ASPECTS OF NA.TUBE IN SOUTHERN PEETJ. 



BY WILLIAM BOLLAERT, F.E.G.S. 



In order to illustrate some points of physical geography, 

 I intend to take the reader to Peru, by the same route 

 by which I went, namely, from England round Cape Horn, 

 sighting its coast off Arica, in latitude 18° 20' south. I had 

 experienced every species of temperature and weather — the 

 cold of a northern winter, the burning, blistering heat in the 

 long calms of the equatorial regions, the frozen seas off Cape 

 Horn; and one series of S.W. gales lasted several weeks, 

 which drove us far to the S.E. with thick and heavy weather, 

 so that when we went on the starboard tack, trusting to clear 

 Cape Horn, on a certain night we got landlocked, a little to 



