The Lake and Brook Lampreys of New York 435 



hold good for the lake lampreys generally in the spawning sea- 

 son, and expressed in words the table shows that the differences 

 are as follows : (i), That the average length of the male and 

 the female lake lamprey is approximately the same, being a 

 little greater in the male. (2), The distance of the base of the 

 first dorsal fin from the tip of the head is considerably greater 

 in the female than in the male, or in other words the first dor- 

 sal fin is nearer the head and farther from the tail in the male 

 than in the female. (3), In like manner the distance from the 

 tip of the head to the vent is considerably greater in the 

 female than in the male, that is, the abdominal cavity is con- 

 siderably more extended in the female than the male, and, (4), 

 the tail is consequently shorter. This table shows also, as do 

 the others, the very great individual variation, so that any 

 conclusion which might be drawn from the averages in the 

 table might be invalidated in any individual case. It seems 

 to the writer, therefore that for the determination of species of 

 lampreys, the proportions of fixed parts of the body are not 

 of great value. 



Upon comparing the averages in the table for the non- 

 spawning lake lampreys there appears the remarkable fact 

 that, apart from the average greater total length of the male, 

 the proportions are exactly reversed from those obtaining in 

 the spawning season and the dorsal fin in the female is some- 

 what nearer the head than in the male, the abdomen shorter 

 and the tail longer.* 



In order to increase the range of comparison, tables are 

 added of the just transformed lake lamprey, larvae, and the 

 true sea lamprey. 



A glance at the averages for the just transformed lamprey 

 will show that its tail is relatively longer than in the adult, 

 the abdomen shorter, and the first dorsal fin nearer the head. 

 The averages given for the larva are more nearly like those of 

 the non-spawning adult than are those for the just tran.sformed 

 ones. 



*The results obtained in this table were so unexpected that all of the 

 specimens were re-examined and remeasured to make sure that the 

 females had not been put inadvertently in the column marked males. 



