631 



The nuclei stain very quickly and intensely with magenta. The 

 white corpuscles are of about the same size as those of Man. They 

 are irregular or amoeboid in shape, and have a very large granular 

 nucleus. Sometimes the whole corpuscle is granular, and devoid of 

 a nucleus. The white corpuscles are remarkably numerous, being not 

 less than three-fourths as numerous as the red, and sometimes equalling 

 them in number. 



In Petromyzon marin us I find the red blood - corpuscles to 

 be circular , as stated. They measure about 0,013 to 0,014 mm in 

 diameter; Gulliver gives 0,019 for Petromyzon, but he very probably 

 used another species. The nucleus is small, placed not in the centre, 

 but near the edge of the corpuscle, and stains very slowly and feebly 

 in magenta or haematoxylin. The white corpuscles are even more 

 numerous than in Myxine, being actually three or four times as many 

 as the red. Their nuclei are small and stain well, and forms tran- 

 sitional in shape and size to the red corpuscles seem to be re- 

 cognizable. Some indeed are round, clear, with excentric nucleus, and 

 similar in size to the red corpuscles; others are quite small, one half 

 the diameter of the former, and with a central nucleus; others again 

 are large, granular, and with the nucleus disproportionately large. 



In both genera the red corpuscles are very easily deformed. The 

 corpuscles of Myxine often seem to taper off to a point at each 

 end, and those of Petromyzon are often (especially in very fresh 

 specimens!) irregular in outHne. 



We thus find that the blood differs in almost every point in these 

 two animals, viz. in the size and shape of the red corpuscles and in the 

 character of their nuclei; and that Petromyzon in these respects 

 stands alone, while Myxine resembles other fishes and especially the 

 Dipnoi and Elasmobranchs , whose corpuscles are much larger than 

 those of Teleostei. But the two genera agree in the extraordinary 

 number of the white corpuscles, which in ordinary fishes are if any- 

 thing exceptionally scanty. 



One more point, of a very curious kind, remains. Shipley in his 

 recent paper on the Development of the Lamprey (Q. J. M. S., Ja- 

 nuary 1887) states, without further remark, that the red corpuscles 

 of the Ammocoete (P. fluviatilis) are oval; and in writing to me 

 he confirms the statement that the corpuscles of the Ammocoete 

 differ altogether in size and form from those of the adult Petromyzon. 

 This observation is, I fancy, quite novel: and it recalls the similar 

 but far less striking fact that the corpuscles of the young tadpole 

 were long ago observed (by Gulliver) to differ somewhat in size 



