354 NOTES. 



Note XI., Chapter III., p. 110. 



THE FUNCTIONS OF THE NEKVOUS SYSTEM OF THE 



CRAYFISH. 



Mr. J. "Ward, in his " Observations on the Physiology of the Nervous 

 System of the Crayfish," (Proceedings of the Royal Society, 1879) has 

 given an account of a number of interesting and important experiments 

 on this subject. 



Note XII., Chapter III. p. 124. 



THE THEORY OF MOSAIC VISION. 



Oscar Schmidt ("Die Form der Krystalkegel im Arthropoden Auge : " 

 Zeitschrift fiir Wissenschaftliche Zoologie, XXX. 1878) has pointed out 

 certain difficulties in the way of the universal application of the theory of 

 mosaic vision in its present form, which are well worthy of consideration. 

 I do not think, however, that the substance of the theory is affected by 

 Schmidt's objections. 



Note XIII., Chapter III., p. 135. 

 THE SPERMATOZOA. 

 Since the discovery of the spermatozoa of the crayfish in 1835-36 by 

 Henle and von Siebold, the structure and development of these bodies 

 have been repeatedly studied. The latest discussion of the subject is 

 contained in a memoir of Dr. C. Grobben (" Beitrage zur Kenntniss der 

 mannlichen Geschlechtsorgane der Dekapoden : " Wien, 1878). There 

 is no doubt that the spermatozoon consists of a flattened or hemi- 

 spherical body, produced at its circumference into a greater or less 

 number of long tapering curved processes (fig. 34 F). In the interior 

 of this are two structures, one of which occupies the greater part 

 of the body, and, when the latter lies flat, looks like a double ring. 

 This may be called, for distinctness' sake, the annulate corpuscle. The 

 other is a much smaller oval corpuscle, which lies on one side of tbe 

 first. The annulate corpuscle is dense, and strongly refracting ; the oval 

 corpuscle is soft, and less sharply defined. Dr. Grobben describes the 

 annulate corpuscle as " napfartig," oi cup-shaped ; closed below, open 

 above, and with the upper edge turned inwards, and applied to the 

 inner side of the wall of the cup. It appeared to me, on the other 

 hand, that the annulate corpuscle is really a hollow ring, somewhat 



