90 F. M. BALFOUR AND W. N. PARKER. 



series of sections on the adult anatomy and development of 

 various organs. 



The Brain — The authors give a fuller description of the 

 adult brain than previous anatomists. The new features in 

 this description are (1) that the parts identified by previous 

 anatomists as the olfactory lobes, are really parts of the 

 cerebral hemispheres ; the true olfactory lobes being small 

 prominences at the base of the olfactory nerves ; (2) that 

 there is attached to the roof of the thalamencephalon a 

 peculiar vesicle, which has not hitherto been noticed, but 

 which is similar to the vesicle found by Wiedersheim on the 

 roof of the thalamencephalon of Protopterus. They further 

 show that the cerebrum is divided into a posterior portion, 

 "with an unpaired ventricle, and an anterior portion in 

 which the ventricle is paired. They consider the presence 

 of a portion of the cerebrum with an unpaired ventricle to 

 be an indication that this part of the brain retain characters 

 which are only found in the embryonic brain of other 

 groups. They point to the presence of lobi inferiores on the 

 infundibulum, of tori semicirculares in the mid-brain, and 

 of a large cerebellum as indications of an affinity between 

 the brain of Lepidosteus and that of Teleostei. In the 

 embryological section full details are given as to the develop- 

 ment of the thalamencephalon, the pineal gland, the cerebrum, 

 and the olfactory lobes. 



At tlie end of the section the characters and affinities of 

 the Ganoid brain are dealt with at some length ; and the 

 authors attempt to show that brains of Ganoids are distin- 

 guished (1) by the large size of the thalamencephalon, and 

 (2) by the cerebrum being divided into an unpaired portion 

 behind and a paired portion in front. 



Organs of Special Sense — Olfactory Sacs. — An account is 

 given ,;pf the development of the olfactory sacs, in which 

 these \acs are shown to originate as invaginations of the 

 nervous layer of the epiblast; the communication between 

 the sacs and the exterior being effected by the rupture or 

 absorption of the superficial epidermic layer of the epiblast. 

 The double opening of these sacs in the adult is described as 

 arising from the division of the primitive single opening. 

 The olfactory nerve arises as an outgrowth of the brain prior 

 to the first differentiation of the olfactory bulb as a special 

 lobe of the brain. 



Eye. — In the adult eye a vascular membrane is described 

 bounding the retinal aspect of the vitreous humour. This 

 membrane is supplied by an artery piercing the retina close 

 to the optic nerve, and the veins from it fall into a circular 



