The Lake and Brook Lampreys of New York 475 



In a larva 73 mm. long, the average diameter was 12.44/x — 

 that is, 0.96/x smaller than in the larva of 142 mm. given in 

 the table. Gulliver ('62-'75, p. 845) states that there is little 

 difference between the blood-corpuscles of Petromyzon planeri, 

 P. fluviatilis, and Ammoccetes branchialis [the larval form] ; 

 that one description may serve for all three of them ; and gives 

 the following measurements : Diameter of the red corpuscles, 

 11.9 /A ; thickness, 4.09 ft. ; diameter of nucleus, 3.96 /x. K61- 

 liker gives 11.3/x.as the size, not mentioning the species or 

 the age. Welcker ('63), gives 15 ;u as the average size of the 

 red corpuscles of Petromyson marinus, with a maximum of 

 16 IX and a minimum of 13.4 /n. Thickness of the corpuscles, 

 3 /i. For the larva the average is 11.7 /x, with a maximum of 

 12.4 yu. and a minimum of 10.9 /x. Thompson ('87), gives the 

 size of the red corpuscles of Petromyson marijins as 13 /x to 

 14 /x. Welcker gives the number of red corpuscles in a cubic 

 millimetre of the blood of P. marimis as 133,000. 



In my own studies, which have extended through several 

 years and have considered specimens at various seasons, the 

 statements of Gulliver are not wholly verified. On the other 

 hand, as shown in the table, the red corpuscles increase in size 

 with the increase in size of the whole animal. This is most 

 marked in larval life. After nearly reaching their full growth as 

 larvse the increase of the red corpuscles to the fully adult condi- 

 tion is only about one micron (i /x), while between the 9 mm. 

 and the 73 mm. larva there is a difference of 5 /x. but only 

 about I |U. between the 73 mm. larva and the one 142 mm. 

 long. This fact of the growth in size of the corpuscles 

 with the growth in the size of the body is again in marked 

 contrast with v^'hat is known of the mammalian red corpuscles, 

 which in the new born and the fully matured differ very little 

 in size. 



The relative number of red and white corpuscles has been 

 determined at various seasons of the year, and while the num- 

 ber of white ones is greater in some specimens than in others, 

 the .season does not seem to affect this ratio very markedly. 

 In general, the lake lamprey has a greater relative number of 

 white ones than the brook lamprey, and in the larva they are 

 more numerous than in the adult. In no case was there seen 



