TRANSACTIONS OF THE SECTIONS. 117 
The branchiz, about twelve-divided, lie across the fore part of the mouth of the 
shell, attached on the left side, where are the heart and branchial veins ; on the right 
is the branchial artery, receiving a large branch from the renal organ situated above. 
Higher still in the shell is the liver with its bile-ducts, and above the liver, in the 
recess of the shell, the testis in-the male and the ovary in the female. The duct 
from each goes downwards ; in the male it opens into a sinus of the integument of 
the right side, where is also seen, at its termination, a little twisted exsertile body, 
but which sinus does not exist in the female, the opening being higher, close to the 
vent, where it is also joined by niditamentary organs; one elongated, the other 
oval, both laminated within, and the latter dark purple without; in microscopic 
structure these seemed to be composed of small globular bodies. 'The testis con- 
tained globules, probably endosmosed spermatozoa; the ovary, evident ova. The 
female specimen was a good deal] the larger, and the tail more obtuse than in the 
male, 
On the Albuminoid Substances of the Blood-corpuscles. 
By Professor Hrynstvs. 
On the Nomenclature of Mammalian Teeth and the Teeth of the Mole. 
By E.R. Layxester and H. N. Mosety. 
The authors pointed out the arbitrary and misleading nature of the division of 
teeth into incisors, canines, premolars, and molars, since to these terms might 
fairly be added sectorial, bicuspid, tricuspid, laniary; secondly, they show that 
maxillary and premaxillary are the only divisions admitting of homological identi- 
fication, the maxillary teeth being further divided into an anterior and posterior 
series in most diphyodonts, by means of the fourth so-called premolar. They 
pointed out that there is no homology of upper with lower jaw teeth, and that the 
present rule for their identification is most arbitrary and unscientific. They show 
that the so-called canine of the mole is a premaxiliary tooth, that animal being 
thus. the only placental mammal with eight premaxillary or incisor teeth. The 
authors further describe a new tooth in the badger, making its dentition identical 
with that of the glutton; this tooth belongs to that series of “ premolars” which 
have no milk-predecessors as described by Mr. Flower recently in the dog and pig, 
and very rapidly drops out of the jaw. 
Notes on the Homologies and Comparative Anatomy of the Atlas and Axis. 
By Avexanver Macatrister, L.R.CS.L. 
It seems to be a principle in morphology that the greater the amount of special- 
ization of function manifested by any organ, the further does the structure so spe- 
cialized depart from the form of the primordial type to which it belongs. This 
principle is particularly exemplified in the case of the two upper cervical verte- 
bre, the atlas, and the axis, as on account of the special varieties of motion of this 
region it is in some instances difficult to assign to the parts of these bones their 
exact positions as serial homologues of the processes in other vertebral segments. 
We owe much of our knowledge of the relations of these hones to Cwen, Rathke, 
Cleland, and Robin; but a few points yet require to be wrought out with reeard 
to them, so as to enable us to understand more clearly the homologies of their 
several portions. In order to present a more complete series of relationships be- 
tween these bones and the ordinary cervical vertebrae, the points to be consi- 
dered are the following :—(1) the nature and homologies of the body, of the axis, 
and of the odontoid process; (2) the nature of the preodontoid half-arch of the 
atlas; (3) the serial homologies of the transverse atlantal ligament and of the 
occipito-axial or check ligament; (4) the third occipital condyle of Meckel and 
Halbertsma; (5) the articular processes of the atlas and axis; and (6) the 
transyerse processes of the cervical vertebre in general, and of these two in par- 
ticular. 
