Proceedings of the Association of American Anatomists IX 



THE TOTAL FOLDS OF THE FOREBRAIN, THEIR ORIGIN AND DE- 

 VELOPMENT TO THE THIRD WEEK IN THE HUMAN EMBRYO. 

 By SusAXNA Phelps Gage. Laboratory of Histology and Emhryology, 

 Cornell University. 



The first pair of total folds appears in birds and lower forms when 

 the flat neural plate is molded over the blind end of the enteron. With 

 the growth of the neural plate and its dipping downward over the end of 

 the enteron, these folds are carried Avith it. This early association of 

 enteron and nonral plate is soon lost, the notochord first and the meso- 

 derm later intervening between the end of the enteron and the part of 

 the neural plate just mentioned. These first neural folds later be- 

 come the albicantial folds and in mammals (man and cat) are relatively 

 most conspicuous Avhen the gill clefts are at their height of development 

 (third to fifth week in man). In man wdiile the neural plate is growing 

 forward, but is still widely open (Homo 12, Johns Hopkins University 

 Collection), these albicantial folds and those giving the first indication 

 of eyes can be seen. As the plates further coalesce (Homo 714, Harvard 

 University embryological collection), in addition to the above folds 

 and nearer the margin of the plate, are two pairs of folds representing 

 the olfactory and diencephalic regions. With the final closure of the 

 plate to form the neural tube (Homo 209, Johns Hopkins University col- 

 lection), the four pairs of folds already formed, albicantial, visual, 

 olfactory and diencephalic, unite to form corresponding lobes. 



At three weeks, there being still a remnant of the neuropore which 

 marks the point of the closure of the neural tube (Homo 148, Johns 

 Hopkins University collection), these four lobes show further differentia- 

 tion: (a) the albicantial being divided into (1) the albicantial and (2) 

 h}^ophyseal folds; (b) the visual being divided into (3) the eye vesicle 

 and (4) the eye stalk; (c) the olfactory divided into (5) the striatal, 

 (6) the olfactory and (7) the cerebral folds; (d) the diencephalic divided 

 into two folds (8 and 9). That is, at the end of three weeks the main 

 folds seen in the forebrain are already outlined. 



The human embryos above mentioned were placed at my disposal by 

 Drs. 3Iall and Minot for comparison with the large series of mammalian 

 and immammalian material in the embryological collection of Cornell 

 University. 



THE DEVELOPMENT OF THE PARAPHYSIS AND THE PINEAL 

 REGIONS OF NECTURUS. By Joiix Warkex. Embryological Labora- 

 tory, Harvard Medical School. 



The paraphysis appears first in an embryo of 12 mm. as a small 

 diverticulum from the roof of the forebrain anterior to the velum 



