140 



SCIENCE. 



FN. S. Vol. YIII. No. 187. 



mony to the favor in which it is held by students 

 in its own language, and it can be safely pre- 

 dicted that the new English translation will 

 gain a large following among students of medi- 

 cine in English-speaking countries. The work 

 of the translators can be commended freely and 

 that of the publishers equally. 



Simon Flexner. 

 Johns Hopkins University. 



SOCIETIES AND ACADE3IIES. 



ZOOLOGICAL CLUB, UNIVERSITY OF CHICAGO. 



MEETINGS OF THE SPRING QUARTER, 189S. 



THE METAMERISM OF HIRUDO MEDICINALIS. 



Results were obtained by the use of gold 

 chloride and methylen blue. 



The typical somite consists of the double 

 nerve cord, Faivre's nerve, Leydig's cells, six 

 ganglionic sacs, and two pairs of nerves, the 

 anterior of which carries accessory ganglia. 

 The anterior nerve is the principal sensory one, 

 innervating all the ventral sense organs and the 

 marginal and outer lateral on the dorsal side. 

 The posterior nerve innervates the inner 

 lateral and the median sense organs of the 

 dorsal side. The innervation is pentannulate 

 and dimeric, the two posterior rings of one 

 somite being united with the three anterior 

 rings of the next somite in the innervation. 



The anal ganglion is clearly made up of seven 

 somites, as indicated by the forty-two gangli- 

 onic sacs and the seven pairs of double nerves. 

 The brain, including the supra- and sub-oeso- 

 phageal ganglia, is likewise composed of seven 

 fused somites. This is proved by the presence 

 of forty-two ganglionic sacs and also by the 

 peripheral distribution of the nerves. Alto- 

 gether, then, the body of Hirudo consists of 

 thirty-five segments, seven in the head, twenty- 

 one in the body and seven in the caudal region. 

 V. E. McCaskill. 



THE AXES OF THE ANNELID EGG. 



The unfertilized egg of Arenicola cristata is 

 flattened and elongated, thus possessing three 

 axes of unequal lengths — approximately 

 1:1.8:2.2. The germinal vesicle lies somewhat 

 nearer one end of the shortest axis and thus 

 furnishes the only means of orientation at this 



time, since the cytoplasmic structure is uni- 

 form. Direct proof of the coincidence of these 

 axes with those found at later stages is thus 

 impossible, but the probability of coincidence 

 is great. 



At the time of formation of the first polar 

 spindle the relations of the axes are 1:1.66:2.00 i 

 after fertilization and before cleavage and in the 

 resting stages of two and four cells 1:1.37:1.50, 

 eight cell stage 1:1.27:1.27. 



In all cases the polar axis is the shortest, and, 

 after cleavage begins, the longest axis is always 

 parallel to the second cleavage plane and the 

 third axis parallel to the first cleavage plane. 

 Thus the first cleavage-spindle lies in the 

 longest axis. In later stages the egg approaches 

 a spherical form. The constancy of the axes 

 in all cases where orientation is possible fenders 

 it extremely probable that they are always 

 constant. The two long axes coincide with 

 none of the axes of the adult, but are parallel 

 with the first two cleavage planes. 



C. M. Child. 



Reviews and other papers presented during 

 the quarter : ' Professor Minot on the Ancestry 

 of Vertebrates,' A. L. Treadwell ; 'Spermato- 

 genesis of the Rat ' (von Lenhossek), M. F. 

 Guyer ; ' Finer Anatomy of the Nerve Cell ' 

 (van Gehuchten), G. W. Hunter ; ' Origin and 

 Variation of the Wing-bars of Pigeons,' Dr. C. 

 O. Whitman ; ' Structure and Development of 

 the Lens in Lower Vertebrates ' (Rabl), Miss 

 E. R. Gregory ; ' Luminous Organs of Verte- 

 brates,' Dr. S. Watas6 ; ' Cell-Lineage and An- 

 cestral Reminiscences ' (Wilson), A. L. Tread- 

 well ; ' The Placentation of Perameles ' (Hill), 

 Dr. W. M. Wheeler ; ' The Eyes of Amphi- 

 oxus ' (Hesse), Dr. W. M. Wheeler. 



NEW BOOKS. 



The Nature and Development of Animal Intelli- 

 gence. Wesley Mills. New York, The 

 Macmillan Company. 1898. Pp. x + 307. 

 $2.00. 



An Illustrated Flora of the United States, Canada 

 and the British Possessions. N. L. Britton 

 and Addison Brown. New York, Charles 

 Scribner's Sons. 1898. Vol. III. Pp. xiv+ 

 588. $3.00. 



