332 
be by one or other of three types as follows: In type I the two zocecia are 
separate throughout their entire length, only touching at their bases. In 
type II they are contiguous throughont their length, and in the interme- 
diate type they are contiguous for part of their length. To a large extent 
correiated with these types of dichstomy is the angle of divergence of the 
branches. 
In all the Jurassic stomatoporas and in a few proboscinas the first 
dichotomy is according to type I, and at a very wide angle (180°). The 
second dichotomy, in the majority of cases, is also according to type I, 
with an angle of 120°. The next is commonly only 90°, the next 60°, and 
the next 45°. all according to type I. “In primitive [Jurassic] forms the 
branching never gets beyond type I with a small angle. In the majority 
of forms, however, sooner or later the intermediate type of branching comes 
in, and in a great many forms this type is the final one. In a few cases of 
Stomatopora, and in all Proboscina, type Il is at some time or. other 
reached, and remains the ultimate form of branching of the zoarium. This 
sequence namely, Type I—Intermediate type—Type II, is invariably 
followed.” (35). 
In primitive Proboscinad (a genus derived from Stomatopora) the first 
dichotomies are according to type 1. “In the typical forms of Proboscina 
the early stages have been so condensed according to the law of accelera- 
tion (Tachygenesis), that the first dichotomy is formed on type II. 
In the mere advanced types of Proboscinw . . . . the ar- 
rangement of peristomes is irregular from the first.” This is the typical 
arrangement for Bernicea, a derived genus of which Stomatopora and 
Proboscina are the first two terms. It is worthy of notice that while in 
the Jurassic forms of Stomatopora type II is not very common, it is ex- 
tremely common in the Cretaceous forms.’ 
Graptolites—The beautiful researches of Ruedemann in this group 
have shown us, as pointed out above, that the graptolite colony closely 
approaches the morphologic value of an individual, and that. like the in- 
dividual, it presents definite ontogenetic (astogenetic) stages. Ruedemann 
(47) applies to the colonial development the terminology proposed by 
'For studies in the zoarial development of Bryozoa see Cumings, BE. R., The 
development of some Paleozoic Bryozoa, Am. Jour. Sei., vol. xvii, 1904; Develop- 
ment of Fenestella, Am. Jowr. Sci., vol xx, 1905. Lang, W. D., The Jurassic 
forms of the ‘genera’ Stomatopora and Proboscina, Geol. Mag., Dec. v, vol. i, 1904; 
The Reptant Eleid Polyzoa, Geol. Mag. Dec. vy, vol. iii, 1906; Stomatopora antiqua, 
Haime, and its related Liassic forms, Geol. Mag., Dec. v, vol. ii. 1905. 
