ITS DIFFERENT PHASES OF DEVELOPMENT IN THE ANIMAL SERIES. 91 
14. Structure of the Nucleated Cell. — By the action of water, the nucleated cell is 
distended and rendered circular even after it has shot out processes and acquired a 
stellate appearance. During this action of the water, the processes of the cell-wall 
mav be observed to become broader and shorter, and to run into each other until the 
outline of the whole cell is circular, as in fig. 10. Within the cell thus distended, the 
celleeform nucleus is seen circular, and about 3-5^0 th °f an inch in diameter. 
15. By the addition of dilute acetic acid, the nucleated cell is not further materially 
affected. 
16. Although a decided coloured stage of nucleated cell does not exist in the blood 
of the Crab, it is proper to observe that many of the nucleated cells transmit the 
light through their interior of a very slight red tint. The circumferential doubling 
of the cell-wall transmitting the light quite colourless, forms with the interior 
a well-marked contrast. Though the red tint is more marked by lamp-light, it is 
sufficiently distinct by day-light. It has been above mentioned, that when the 
corpuscles collected in a mass are viewed by reflected light, they also appear slightly 
pink. 
17. Besides granule-cells and nucleated cells such as have now been described, cells 
occur in which the cellaeform nucleus is already visible, but still surrounded by some 
granulous matter (fig. 11.). These may be viewed as cells in a state of transition 
from granule to nucleated cell. 
18. It may thus be concluded, that in Crabs the blood-corpuscle presents itself in 
two different phases of development, as in the oviparous Vertebrata, viz. the phases 
of granule-cell and of nucleated cell, the granule-cell being the first phase of deve- 
lopment, the nucleated cell the second phase. 
19. Floating about amongst the blood-corpuscles, there are seen a few elementary 
granules, the larger of which, from gqys'oth to 1 2 ooo ^ 1 an ’ n diameter, have 
the form of biconcave circular discs. 
Blood-corpuscles of the Lobster. 
20. The description which has now been given of the blood-corpuscles of the Crab, 
is in all respects applicable to those of the Lobster*. 
E xamination of the Blood-corpuscles of Arachnida. 
21. It was the common Spider the blood of which I examined ; and the mode in 
* The changes of form which the blood-corpuscles of the Lobster, like those of the Crab, undergo after the 
blood is drawn, were described and delineated by Hewson as accurately as his microscope appears to have 
enabled him to observe them. Hewson also mentions what I have found to be the case, that the blood of the 
Lobster, “ after being some time exposed to the air, jellies, but less firmly than the blood of more perfect animals.” 
In this respect the blood of the Lobster differs from the blood of the Crabs which I examined ; the blood of 
the latter, as I have above stated, not containing a sufficient quantity of spontaneously coagulable material to 
form a perfect clot. It may be proper to remark that it was in the beginning of winter when I examined the 
Crab’s blood, and in the beginning of spring when I examined that of the Lobster. 
