THE FISSURA HIPPOCAMPI S81 
GENERAL MORPHOLOGY 
The 11.8-mm. embryo, Mall Collection, 1121 (figs. 7, 8, 9, 11) 
So far as the nervous system is concerned, this embryo lies 
between the 6.9-mm. embryo of His (Br.) and his embryo C. R. 
(13.6 mm. N. L.). It is a thin-walled tube easily divided into 
TABLE 1 
Embryos described in this contribution 
NUMBER eae COLLECTION CONDITION SOURCE FIXATION ee 
mm. fu 
PDT LIES Mall Good Abortion Corrosive sub- | 40 
limate 
940 | 14.0 Mall Excellent | Abortion Formalin 40 
(10.0 
in alc.) 
H173 | 19.1 Chicago | Excellent | Abortion Formalin- 10 
Zenker 
460 | 21.0 | Mall Excellent | Abortion Sublimate- 40 
(20.0 acetic 
in alc.) 
H91 | 27.8 Chicago | Fair Abortion 10 per cent 20 
in for- formalin 
malin. 
H41 | 32:1 Chicago | Fair Abortion 10 per cent 20 
in for- formalin 
malin. 
H163 | 39.1 Chicago | Excellent | Operation for | Formalin- 20 
: fibroids Zenker 
886 | 43.0 | Mall Excellent | Operation 10 per cent for- | 100 
malin and 
Bowen’s 
fluid 
the five brain vesicles of v. Baer. The roof plate is thin in the 
telencephalon and myelencephalon, but not noticeably so in 
the diencephalon and mesencephalon. The floor plate is be- 
ginning to show its characteristic thickenings. ‘The floor of the 
fourth ventricle is long, broad, and shallow. The lateral recess 
is not present. There is no evidence of any increase in thickness 
of its anterior lip. There is an insignificant groove in the floor 
