The Microscope. 



323 



examinations were made with a 2 mm. apochromatic objective and 

 an ocular Xl2. 



That the corpuscles should be circular in the larva as well as 

 the adult is to be expected also on morphological principles, for as 

 far as investigated the red blood-corpuscles of all vertebrates, 

 mammalian as well as non -mammalian, are at first circular in out- 

 line, and become oval, if at all, only at a later stage of development. 

 (12, 8, 10.) 



Table showiug the diameter and thickness of the red blood-corpuscles of 

 lamprey eels in the adult and larval condition ; also the relative number 

 of red and white corpuscles, and the number of red corpuscles in a cubic 

 millimeter of blood.* 



Ratio of 

 white to red 

 corpuscles. 



Number of red 



corpuscles in a 



cubic millimetre. 



Male, 1:20 Male, 391,383 

 Female. 1:15 Female. 334,666 



1:95 

 1:10 



1:10 



500,000 

 Not determined. 



Not determined. 



Note. — The blood for measurement was taken from the heart or a 

 pithing wound, and mounted without the addition of any liquid. The 

 cover-glass was supported by a hair, and sealed with castor oil. Only undis- 

 torted corpuscles were measured. The averages were obtained from twenty- 

 five measurements in each case. All measurements were made with a 2 mm. 

 apochromatic objective and C. ocular containinf^ a Jackson ocular micrometer, 

 the value of which was determined by using a Rogers standard stage 

 micrometer. 



*In a larva 73 mm. long, the average diameter was 12.44 //—that is, 0.96 // smaller 

 than in the larvi of 143 mm. given in the table. Gulliver (4, p. 81.5) states that " there is 

 little difference between the blood-corpuscles of Petromyzon plaiieri, 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, 119//; 

 thickness, 4.09 /*; diameter of nucleus, 3.96/'. Kolliker (9) gives 11.3// as the size, not 

 mentioning the species or the age. Welcker (20) gives 15 // as the average size of the red 

 corpusclej of Petromyzon marinus, with a maximum of 16 f- and a minimum of 13.4 /*. 

 Thickness of the corpuscles, 3 //. For the larva the average is 11.7 //, with a maximum of 

 12.4/^ and a minimum of 10.9 //. Thompson (17) gives the size of the red corpuscles of 

 Petromyzon marinus as 13 // to 14 /*. He says also that the number of white corpuscles is 

 three or four times as great as the red ones . Welcker gives the number of red corpu^.cles 

 in a cubic millimeter of the blood of P. marinus as 133,000. 



