1894.] Schulze’s System of Descriptive Terms. 373 
the planes parallel to this are “ paratransversan.” If the 
suggestion were adopted, all parts lying internally in these 
planes would be meridien and transversen, and the points on 
the periphery also in these planes would be meridian and 
transversan. 
He intimates that there are oral and “aboral” planes in the 
paratransversan planes, but does not advocate the use of the 
terms oran, orad, and aboran and aborad as desirable for those 
bodies having the mouth in what may be called the terminan 
paratransversan plane, and the anus or base in the opposite 
plane. 
Among Porifera one can assume a central axis, and it is 
possible to distinguish the oral and aboral ends or what may 
be considered as corresponding to them, the excurrent aper- 
tures (or so-called oral openings) and the attached base. But 
the incurrent apertures, the digestive sacs, the tissues and the 
spicules of the skeleton are normally arranged in concentric 
layers, which cannot be referred to any system of imaginary 
planes parallel with the principal axis. There is in these 
forms no organic element by which a meridian plane can be 
determined, they are exclusively concentric. 
The same remarks apply also to the Hydrozoa and Actino- 
zoa and more or less to all of the animals included under the 
_ old term, Radiata, whose parts are normally arranged in con- 
centric layers cut by radiating lines and planes. If Schulze’s 
system had taken note of such general morphic characters 1t 
would have been more complete: The meridian plane can be 
organically determined in most of these organisms, but this 
primitive division of the body is not carried out in the struct- 
ures of the sides, these have no organic lateral parts which van 
be advantageously compared with any supposed parameridian 
planes. They and the tissues of the body all lie in concentric 
tubular conical or spherical surfaces secondarily intersected by 
radiating lines and planes. . Schulze’s system of planes takes 
no notice of these facts, but his meridian and transversan 
planes can be used with advantage to indicate the existing 
bilateral elements in these structures. The main objection to 
his system appears to be that it is better fitted for use among 
