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VI. The Blood-corpuscle considered in its different Phases of Development in the 
Animal Series. Memoir III . — Comparison between the Blood-corpuscle of the 
Vertebrata and that of the Invertebrata. By T. Wharton Jones, F.R.S., Lec- 
turer on Anatomy, Physiology and Pathology, at the Charing- Cross Hospital, 8$c. 
Received May 7, — Read June 19, 1845. 
i. In instituting a comparison between the blood-corpuscle, in its different phases 
of development, of the Vertebrata and that of the Invertebrata, it is obvious that the 
examples first taken for the purpose ought to be selected from the lowest class of 
the oviparous Vertebrata on the one hand, and from the highest class of the highest 
division of the Invertebrata on the other. 
2. In accordance with this I proceed to compare together the blood-corpuscies of 
the Skate and Crab. 
Comparison between the Blood-corpuscle of the Shate and that of the Crab. 
3. From the observations above related, it results that the blood-corpuscle of the 
Crab resembles that of the Skate in presenting two different phases of development, 
viz. the phase of granule-cell and the phase of nucleated cell, and that in these two 
phases respectively the essential points of structure are the same. 
4. The blood-corpuscle of the two animals, however, differs in the degree of deve- 
lopment which it attains in the phase of nucleated cell. In the Crab its development 
is arrested at the uncoloured stage, or at the most at the commencement of the co- 
loured stage. But this absence of nucleated cells in the decided coloured stage in 
the blood of the Crab, it has been seen is a peculiarity which there is reason to be- 
lieve is presented by one at least from among oviparous vertebrate animals, viz. 
Branchiostoma lubricum. 
5. The blood of this fish may therefore be admitted as probably differing but little 
in the character of its corpuscles from the blood of the Crab, and as constituting in 
this respect a transition from the Vertebrata to the Invertebrata. 
6. Having thus compared the blood-corpuscle of an animal from the lowest class 
of oviparous Vertebrata with that of one from the highest class of the highest divi- 
sion of the Invertebrata, we are prepared to institute a comparison between the blood- 
corpuscle of the oviparous Vertebrata generally, and that of the Invertebrata from 
Crabs to Mussels. 
MDCCCXLVI. p 
