98 Transactions of the Royal Microscopical Society. 
of time short enough for any observer to witness it under the 
microscope, the process of development or transition can only be 
studied by making certain deductions from the various transitory 
forms of these blood-corpuscles as they are met with in the blood 
of the animal. 
In the blood of the adult animal, the primary form of the 
colourless blood-corpuscle seems to be a nucleus surrounded by a 
layer of granular protoplasm (Fig. 39, a). The nucleus represents 
a vesicle, distinguished by a distinct double contour, and containing 
a limited number of granules. Both contour and granules show a 
faintly greenish tint. The multiplication of the corpuscle takes 
place by a division of the nucleus, while it is still surrounded by 
the protoplasm (Fig. 39, a and h), though many instances are 
observed where the nuclei are set free by the dissolution of the 
protoplasm (Fig. 39, c), and hence a number of free nuclei are 
always met with in the blood. The transitory forms to be studied 
are represented in Fig. 40. The first {a) is a round nucleus, in 
which the inner contour of its wall is represented by a zone of 
minute granules of a greenish tint, appearing as if deposited upon 
the inner surface of the wall ; in the interior of the body the usual 
granules are observed. The second form (h) represents a larger 
Fig. 43. — Coloured blood-corpuscle of the young Amphiuma. 
Fig. 44. — Coloured blood-corpuscle with its protoplasm contracted, from the 
young Amphiuma. 
Fig. 45. — Egg of the Amphiuma with embryo (natural size). 
Fig. 46. — Embryo of Amphiuma, taken from the egg (natural size). 
Fig. 47. — The same, slightly enlarged. 
Fig. 48. — Coloured blood-corpuscles of the large Bull-frog ; a, front view ; 
6, side view. 
Fig. 49. — A coloured blood-corpuscle of the same animal, in which a retrac- 
tion of the protoplasm has taken place, exposing the membraneous layer. 
Fig. 50. — Coloured blood-corpuscle of the Frog, with spinous elevations on its 
sm’face. 
Fig. 51. — Coloured blood-corpuscles of the Frog, treated with water. 
Fig. 52. — One of the same, treated subsequently with a weak solution of 
chromic acid. 
Fig. 53. — Coloured blood-corpuscle of the Frog, treated with acetic acid vapour. 
Fig. 54. — Coloured blood-corpuscles of the Frog, treated with a weak solution 
of chromic acid. 
Fig. 55. — Coloured blood-corpuscles of the Frog, treated with a strong solution 
of hydrate of chloral. 
Fig. 56. — Coloured blood-corpuscles of the Tree-frog ; a, front view ; 6, side 
view ; c, one with a portion wanting, as described in the text. 
Fig. 57. — Coloured blood-corpuscles of the Tree-frog, treated with a weak 
solution of chromic acid ; a, corpuscle with the protoplasm contracted in the form 
of a star ; 6, the protoplasm entirely contracted upon the nucleus ; c, granular 
appearance of the protoplasm. 
Fig. 58. — Infusorium found in the blood of the Tree-frog. 
Fig. 59. — Coloured blood-corpuscles of Man ; a, front view ; 6, side view. 
Fig. 60. — Various forms of coloured blood-corpuscles of Man, produced by a 
partial contraction of the protoplasm. 
Fig. 61. — Coloured blood-corpuscles of Man, exhibiting spontaneous motion. 
Fig. 62. — Coloured blood-corpuscles of Man, treated with water. 
