October 25, 1901.] 



SCIENCE. 



627 



Region based upon its Development in 

 Acantliias ' : Charles Sedgwick Minot, 

 LL.D. 



Tlie paper describes the development of 

 the epiphysis, the posterior and superior 

 commissures, the velum transversum and 

 the paraphysis in the embryos of the dog- 

 fish, of from 11.5 to 86.0 mm., studied 

 chiefly by means of median sagittal sections. 

 The velum transversum arises close to the 

 epiphysis, and, unlike other known types, 

 the dog-fish retains this relation perma- 

 nently. The velum gives rise by its lateral 

 expansion to the choroid plexus of the lat- 

 eral ventricles. In front of the velum is 

 the paraphysial arch, which is not identical 

 with the paraphysis. This arch exists in 

 all vertebrates, but has not hitherto been 

 recognized as a constant morphological 

 constituent of the brain. The true para- 

 physis arises as a small evagination from 

 the paraphysial arch, and appears very late 

 in development — in the oldest embryo ex- 

 amined it was not clearly present, so that 

 it is uncertain whether it exists in the dog- 

 fish at all. In amphibia and birds it is 

 easily found, and there develops into a 

 glandular organ, never, so far as known, 

 into a sense-organ, as has been generally 

 assumed hitherto. The single duct opens 

 into the cavity of the brain. We may as- 

 sume, in default of actual knowledge, that 

 the gland supplies a secretion to the brain, 

 being physiologically comparable to the in- 

 fundibular gland of the lower vertebrates. 

 In amphibians the velum transversum ex- 

 pands so much that it grows forward and 

 across in front of the paraphysis ; the en- 

 larged velum is wholly transformed into the 

 adult choroid plexus, as a part of which the 

 paraphysial gland was long regarded erro- 

 neously. In birds and mammals the median 

 portion of the velum is rudimentary or 

 obliterated ; the paraphysial arch is well 

 developed and forms a large part of tela 

 choroidea superior; the later portions, on 



the contrary, are greatly developed to form 

 the lateral plexus. 



3. 'The Essential Mechanism of Hear- 

 ing in Man ' : Howard Ayres. 



4. ' On the DLsappearauce of the Vast 

 Flocks of Wild Pigeons {Ectopistes viigra- 

 toria) in Eastern North America ' : Ed- 

 ward T. Keim, Denver, Colo. 



In the memory of the middle-aged man 

 many facts can be recalled relating to the 

 annual flight of the myriads of wild pigeons 

 through the Eastern, Middle and Central 

 States of the United States of America. 

 The newspapers of that period (1850 to 

 1870 and 1880) teemed with accounts of the 

 vast numbers seen, and the superlative ad- 

 jective was immoderately used to describe 

 the great number and the indiscriminate 

 slaughter. Certain wooded sections in the 

 States of Kentucky, Tennessee, Missouri, 

 Iowa, Illinois, Minnesota and Michigan, 

 when the white settlers first came into these 

 regions, were visited annually by the pigeons 

 for nesting places, but owing to the almost 

 ceaseless attacks by man, beast and bird, 

 these localities were deserted for a year or 

 more. Another fact also observed was that 

 the abundance or scarcity of the ' mast ' 

 and the wild fruits and grains, which con- 

 stituted their main food, determined the 

 location of the annual nesting places. An 

 account of a visit by the writer in company 

 of a party of hunters, to the so-called 

 pigeon roost near Maquoketa, Jackson 

 county, Iowa, will be given, and a map of 

 the United States showing approximate lo- 

 cation of known breeding places will be 

 exhibited. An eflbrt will be made to secure 

 mounted specimens of the male and female 

 pigeon. 



5. ' The Eleven Elements in the Superior 

 Molar Teeth of Mammals ' (illustrated by 

 models) : Henry F. Osborn. 



6. ' The Homologies of the Mouth Parts 

 of Insects with Complete Metamorphosis ': 

 Vernon L. Kellogg. 



