Hyatt] 100 
[April s, 
and {he otlior is a near relative of tlu' primitive ancestral forms of 
the nautiloids in the Paleozoic. One oceans in the paracme and 
the other in the early epacme of the group of chambered 
shells. They are widely distinct in their structural characteristics, 
and these differences are greater in the young than at any sub- 
sequent stage of their ontogeny. Baculites has a close-coiled shell 
in the nepionic stage, as has been lately demonstrated by Dr. 
Amos P. Brown ^ of Philadelphia, and Orthoceras is straight from 
the earliest stage. The return of a similar form in Baculites in 
the epinepionic pei'iods of development in obedience to tlie law of 
the cycle does not carry the structure back M'ith it to a rejietition 
of the orthoceran siphuncle and sutures. 
The structure of an individual during its development might be 
represented gra2:)hically by an irregular spiral of one incomplete 
revolution wliicli describes a curve, continually increasing its dis- 
tance from the point of departiu-e until the meridian of the epliebic 
stage, is reached, and then beginning to return. Such a curve 
would alwaj's as a spiral rise more or less vertically, and con- 
sequently even if it completed the revolution, must terminate in 
space. It might, perhaps, reach nearly to the same imaginar}'^ 
vertical plane, but never to any point approximate to that of its 
departure. Structure separates tlie extremes of life as widely as 
possible and does not permit us to regard them as approximate, 
nor can one regard old age, however complete its return in external 
form, as a reversion. One of the most noteworthy contributions 
of bioplastology is that it gives proper values to this class of 
analogies and shows them to be constantly recurring in the 
individual and in the phylum in obedience to well ascertained laws 
of morphogenesis. 
Further discussion of this point so far as the terms are con- 
cerned is not necessary, since it is now proposed to abandon the 
oMer names and adopt " gerontic," as proposed by Buckman and 
Bather, and also to designate the substages by the same word 
with an appropriate i)refix, ana, meta, or para. 
The different stages have been described by Dr. Beecher among 
Brachiopoda, Dr. Jackson among Pelecypoda, and the author 
among Cephalopoda ; and Buckman and BatJier, and also Blake - in 
1 Proc. acad. iiat. sci., Pliila., 1891, \k 159-IGO. 
'Evoliuinn and classiticatinn of Ciplialopoda, Proc. seol. assoc Lond., v. 12, p. 
270-295, 1892. 
