Students preparing for examinations are frequently troubled by "comparison" questions. Tabulation is often recommended, but we are inclined to favour a rather more flexible plan of marking off differences and resemblances. In tabulation a considerable loss of time is occasioned by writing down the features of both the things compared, and this is a serious consideration for the examinee. We advise him therefore, first, if he possibly can, to draw side by side and in corresponding positions the two things under consideration, and then, going over them in a methodical way, to state simply the difference between each homologous part. We append as examples three test answers actually submitted (with figures) in "Correspondence" work:-- 1. Compare the brain of the frog with that of the rabbit. In the frog's fore-brain-- The olfactory lobes are fused in the middle line. There is no corpus callosum, nor is there a middle commissure to the third ventricle. The cerebral hemispheres are not convoluted, and, looked at from the dorsal aspect, do not hide the thalamencephalon and mid-brain. The pineal gland lies in the cranial wall and not deeply between the hemispheres, and its stalk is longer and tilts forward. In the mid-brain-- The optic lobes are two, instead of being corpora quadrigemina, and hollow. In the hind-brain-- The cerebellum is a very small transverse band, and has no lateral parts. The medulla is relatively larger. There are no spinal accessory nor hypoglossal nerves to the brain. 2. Compare the vertebrae of dog-fish, rabbit, and frog. The centra of the dog-fish are -opistho- [amphi]-coelous (i.e., hollow at either end). The centra of the rabbit are flat-faced. The centra of the frog are procoelous (hollow in front). The notochord persists between the centra in the dog-fish and rabbit, within the centra in frog. The centra of the rabbit have epiphyses, absent in the dogfish and frog. The transverse processes of the rabbit typically bear ribs. Short ribs occur in the dog-fish, but their homology with those of the rabbit is doubtful. The frog has no ribs. The interneural plates are peculiar to the dog-fish in this comparison. 3. Compare the skull of the dog with that of the frog. The Brain Case-- Of the frog is a cylindrical box, from which the otic capsules project conspicuously on either side. It contains only two ossifications in its cartilaginous substance (the sphen-ethmoid and the ex-occipital), being protected by the membrane bones, the parieto-frontals above and the parasphenoid below.