1875.] RED BLOOD-CORPUSCLES. 475 
the significance is intimated of the comparative minuteness of the 
corpuscles in the small species of single natural orders or families of 
Apyrenzemata and throughout the class of Birds. 
Since the publication, upwards of a quarter of a century ago, of 
my Tables of Measurements, I have made so many additions and 
revisions by new observations, several of which have never been pub- 
lished, that nothing short of the present paper will suffice to give 
such a fair view of the whole series of averages as will be most useful 
for future reference, in relation to questions, often arising and likely to 
increase, concerning the import, whether taxonomic or physiological, 
of the sizes of the red corpuscles of the blood. The original Tables, 
which appeared in the ‘ Proceedings’ of this Society (P. Z.S. 1845, 
p- 93) and in the Sydenham Society’s edition of Hewson’s Works, 
8vo, 1846, followed my extensive observations on the same subject in 
the ‘ Lond. and Edin. Phil. Mag.’ January 1840 to August 1842, and 
in the Appendix to the English version of Gerber’s Anatomy, 8vo, 
Lond. 1842. Those measurements have been added to piecemeal 
up to the present year; and the tables from Hewson’s Works were 
converted into French millimetres and transferred by Milne-Edwards 
to the first volume (8vo, Paris, 1857, pp. 84-90) of his great work 
already cited. Of course, as linear measurements only are used, all 
my remarks as to the sizes of the corpuscles are to be understood 
accordingly. 
The measurements now recorded show the results of the labours 
of many years, and are far more copious than any others known to 
me, and, with the observations connected therewith originally, proved 
sundry facts, such as, e. g.: —the singular minuteness in the Tragulidze 
of the red blood-corpuscles, their largeness in the Edentata and pin- 
niped Feree, and batrachian character in Lepidosiren; the compa- 
rative sizes of the corpuscles in several of the subsections of the 
vertebrate subkingdom ; the relation of those sizes to the sizes of 
the species in the orders or families of Apyrenzemata and throughout 
the class of Birds; the essential difference between the Pyrenzemata 
and Apyrenzmata, with the conformity of the Lampreys to the 
former and of the Camels to the latter type, and the identity of the 
corpuscles in placental and implacental Mammalia. On some points 
the engraved page in the ‘ Proceedings of the Zoological Society,’ 
Feb. 25, 1862, contains such errors of omission and commission, caused 
by strange accidents, and is so deficient in later observations, that it is 
now given with the needful corrections and additions in illustration of 
the present paper. Specimens of the corpuscles in the different classes 
and orders are all drawn side by side to a uniform scale, of which each 
one of its ten divisions stands for >) of an English inch, and the 
whole length of the scale for =}¢ of an inch. The same design will 
be adopted, with unimportant modifications in the arrangement of 
the corpuscles and divisions of the scale, in the next edition of Pro- 
fessor Beale’s excellent work on the microscope. Historical notices 
of the observations of my predecessors and contemporaries are given 
in the memoirs cited above, and in the notes to the edition of Hew- 
son’s Works already mentioned. 
