222 J. B. JOHNSTON, 
our knowledge it seems to me that it would be best to give to all 
the decussations in this positition some general name to indicate 
their position, and designate each one by the name of the tract in- 
volved (together with the animal or group in which it has been 
studied and the name of the author when these details are necessary). 
With this in view I have spoken of the decussations behind the 
chiasma as the postoptic decussations. For the several parts of the 
whole decussation I suggest the use of the names decussatio post- 
optica tractus lobo-cerebellaris et bulbaris, dec. postopt. tractus tecto- 
lobaris, ete. 
I can do little more than mention the several other decussations 
in the hypothalamus described by EDINGER. Decussatio infundi- 
bularis, formed by the tractus saccus vasculosus (see next section). — 
Decussatio retroinfundibularis in Reptiles, corresponding in position 
to the premammillary decussation described above (page 138) for 
Acipenser. My study of this has given such unsatisfactory results 
that I can not attempt to determine its character or homology. 
Decussation of ansulate fibres in Reptiles dorsal to the decussatio 
transversa. Commissure of the central grey in Selachians. This is 
possibly the same as the decussatio retroinfundibularis in Reptiles. 
Decussatio suprainfundibularis in birds. F. MAYER (97) mentions 
an infundibular commissure in Petromyzon in which cross part of 
the ascending fibres from the ‘tween brain to the fore brain. 
2. Saccus vasculosus. 
The saccus and hypophysis have been the subject of many em- 
bryological and anatomical investigations which it is unnecessary for 
me to review. The structure in adult Acipenser suggests that there 
is present here, in addition to the ectodermal and infundibular 
portions of the pituitary body described by DourRN (83) and Lunp- 
BORG (94) in Petromyzon, Teleosts and Amphibia, the third or ento- 
dermal portion described by von Kuprrer (93). If so, Acipenser 
agrees with Amphibia and Mammals (von KuPFFER). The mingling 
of the tubes of the infundibular portion with those of the glandular 
portion has not before been described. WALDSCHMIDT (’87) says 
that in Polypterus the hypophysis is very large with numerous 
openings into the infundibulum, but that there is no saccus vascu- 
losus in the sense in which that term is used in Teleosts. The 
numerous openings into the infundibulum show that the tubes of 
the saccus are imbedded in the tissue of the hypophysis. A figure 
