872 Values of the Stages of Growth and Decline. 
VALUES IN CLASSIFICATION OF THE STAGES OF 
GROWTH AND DECLINE, WITH PROPOSITIONS 
FOR A NEW NOMENCLATURE.' 
BY ALPHEUS HYATT. 
ey accord with views brought to the notice of the society in 1884, 
under the title of the “ Larval Theory of the Origin of Tissue,”? 
an abstract of which was subsequently printed in Amer. Journ. Set. 
May 31, 1886, we divide the animal kingdom into thre¢ compre- 
hensive divisions: (1) Prorozoa, unicellular animals, which 
propagate by means of asexual (autotemnic) fission and by spores, 
and build up colonies, but always remain typically unicellular. (2) 
Mesozoa, multicellular colonies, but composed of only one layer of 
cells, so closely connected, that they may be called a primitive tissue, 
and having more or less spherical forms.* They propagate by 
means of ova, spermatozoa, and by autotemnic fission,* and have 
an aula or common cavity, but no specialized digestive cavity oF 
archenteron. (3) METAZOA, complexes of multicellular colonies, in 
which growth by sexual union, and resulting fission of the ovum, 
forms three primitive tissue layers and builds up a body in which 
an archenteron is always developed. They propagate always by 
means of ova and spermatozoa, autotemnic fission occurring only, 
at all, during the earliest stages of the ovum. Holoblastic ova may 
be regarded as the more primitive or generalized forms to which 
1 Abstract of a paper read at’ the meeting of the Bost. Soc. Nat. Hist., 
Nov. 16, 1887. Vol. xxiii. 
* Proc. Bost. Soc. Nat. Hist., vol. xxiii., 1884, p. 45. 
3 See Butschli’s remark that the closely appressed hexagonal cells of 
the envelope are connected with each other by threads of propaplasm. 
Bronn. Thierreichs, vol. i. Protoz., p. 775. 
‘The best summary of all observations is in the work just quoted, 
where Butschli calls the sexual cells ova and tophora, but alludes 
to the cells developing by autotemnice fission as Parthenogonidia. They 
are by his own descriptions and those of others, oya, Which differ from 
POPE ova only in their ability to develop through autote mui 
ion. 
