i897. NOTES AND COMMENTS. 231 



the exact knowledge of crystalline substances which has been gradually 

 and laboriously acquired during the last hundred years. The methods 

 by which crystals grow, their shape and symmetry, and the occurrence 

 of twinning were clearly expounded with the aid of numerous appropriate 

 specimens and of a very beautiful collection of lantern slides. The 

 second lecture was devoted to an able exposition of multitudinous 

 experimental methods which have been applied by crystallographers 

 to the determination of crystalline symmetry ; an opportunity was 

 thus afforded for exhibiting a number of pieces of exact crystallo- 

 graphic measuring apparatus which are unfortunately too seldom seen 

 and even less frequently used in this country. The last lecture dealt 

 mainly with the structure of crystals. This subject, which has only 

 been brought to its present satisfactory state during the last few years 

 by the labours of Fedorov and Barlow, is of so complex a nature as 

 to excite no little wonder at the lecturer's temerity in attempting to 

 present even its barest outlines to a lay audience ; the discourse, 

 however, left little to be desired in point of lucidity and may possibly 

 be of permanent value in destroying some part of the reputation for 

 profundity hitherto enjoyed by the theory of crystal structure. A 

 brief description of a few of the more important applications of 

 crystallography concluded the course. 



The most vivid impression left by these lectures is that the 

 crystallography of to-day with all its far-reaching ramifications con- 

 stitutes a science founded upon a secure mathematical basis, and so 

 securely founded as to rank in this respect beside the better-known 

 exact physical sciences. This being the case, it is difficult to under- 

 stand why a subject of such wide application — which bears so 

 minutely upon the most remote problems of physics and chemistry 

 and which could be so advantageously used as a teaching tool in 

 connection with the geometry of space, spherical trigonometry and 

 many branches of physics and chemistry — does not more frequently 

 find a place in the courses of instruction given at our higher schools 

 and colleges. 



North American Oligochaetes. 



Mr. F. Smith has lately been studying the terrestrial and aquatic 

 Oligochaeta of North America with some success. We have before 

 us {Bull. Illinois State Lab., vol. iv.) the second of his articles on the 

 subject, which includes descriptions of a new Lumbriculid from 

 Illinois and of a new species of Microscolex from Florida. The first- 

 named worm is referred to a new genus Mesoporodrilns, which is of 

 some interest. The most remarkable fact about it is the unilateral 

 development of the male efferent apparatus, which opens in the middle 

 ventral line. It seems to be much like that of Eclipidrilus and Sutroa, 

 in that the atrium is surrounded by the sperm-sac. The spermathecae 

 are two, lying in successive segments, and each opening also on to 

 the middle line. The number of new forms from the North American 



