663 



.3 9 TT) 



of tlie images, i.e. ahnost \/ 1 o\'\/ S=- S'^'^^\ coi-reclly >S'*^'''^- or \ S. 

 In the interesting essay of August Putter ^) I find, in te.xt and 

 in figures, statements both of the retina-surface and of the size 

 of the body of full-grown individuals of Hyperoodon rostratus, 

 the Bottienose-Whale, and of Phocaena communis, the Por[)oise, 

 both Odontocetes. The lengths of the bodies are proportional as 6 : 1, 

 and the diameters of the retina as 2:1. From this follows, that 



/^ NO. I. 33.. j7.5/^> 



those diameters increase as - I = \X -. 



In my memoir of J 897 a Lion was also compared with a Cat for 



the calculation of the exponent of correlation. The exponent of 



correlation 1 found was 0.5466. The coefficient of cephalisation, 



calculated with 0.55 . . , gives therefore a different result for them. 



In order to obtain equality, the S of the Lion must only be a little 



diminished (according to the proportion that presumably existed 



between the two individuals examined by Matthiessen). Then the 



proportion of lengths of the images in the eyes, measured for both 

 18.95 i'-^/S^ 



species, = 



-, is exactly equal to 



11.80 V s 



An equal relation is found between the Sea-eagle and the Hawk. 



The general validity of this relation is especially obvious when 

 comparing little animals with enormously large ones. The shapes of 

 the bodies can then even be greatly different, if only there is no 

 great deviation in the coefficient of cephalisation. Among the animals 

 of which Matthiessen has measured the lengths of the images, are 

 also the Fox, the Oat and the Rabbit. The weights of the bodies of 

 these animals and also of that of Sibbald's Fin-Whale, (of which 

 several individuals ha\'e been examined) are approximately known. 



Between these the following relations are found: 



/ 5 \0.133 



I — I in Kilograms 



Proportion of the 



lengths of the 

 images (in MilHm.) 



Sibbald's Fin-Whale and Fox 



n n I) ^ai 



„ „ „ Rabbit 



Average 



/ 10000 \0i33 _ 

 100000 \0133 



3.643 



3.995 



/ 100000 \ 



/ 100000 \ 0-1 33 

 /_iwuuuj =4.381 



39.78 

 9.42 



39.78 

 11.80 



39.78 

 9.19 



4.006 



4.223 



= 3.371 



= 4.329 



3.974 



') Zoologische Jahrbüclier. Ablheilung fur Anatomie und Onlogenie der Thiere. 

 Jena 1903. p. 240, 243, 278 and 280. 



