Vol.. 8, 1922 
PALEONTOLOGY: R. RUEDEMANN 
55 
Saalfeld^ hold that external influences act first upon the cytoplasm (proto- 
plasm) of the cells, and especially of the germ-cells, producing inceptive 
genes (plasmogenes) which finally become true genes of the heredity- 
chromatin when the long-continued strain has passed a certain "threshold." 
This final abrupt change would well account for the abrupt appearance 
of new characters in the ontogeny, or the salto-mutations of De Vries and 
the constancy of persistent types under stable external conditions. Like- 
wise the fact that the cytoplasm is known to influence the heredity-chro- 
matin of the nucleus, or the genes, would explain the absence of flucto- 
mutations or variations under stable conditions. Persistent types are 
then either forms in which through lack of external stimulation no changes 
arise in the cytoplasm that produce new genes ; that is, forms in which the 
cytoplasm is not able to react any more to external influences and differ- 
entiation could take place only through loss of genes or a combinative 
mode of production of new genes. This latter method leads to so-called 
"self -differentiation" and thereby to the excessive terminal forms of series, 
or to terminal persistent types, in which latter case absolute rigidity of the 
forms would result from the entire failure of acquisition of new genes and 
gerontic rigidity in the old ones. 
The persistent radicles, on the other hand, correspond to the extreme 
development of what Saalfeld, from his studies of ammonites, terms 
"Konservativreihen." These are series in which the salto-mutations ap- 
pear in very long intervals, while the numerous side-branches (which fur- 
nish the index-fossils) develop by rapid salto-mutations. These persistent 
radicles are therefore able to undergo new periods of explosive and cli- 
macteric development (Virenz-perioden of Wedekind) and are thus still 
less absolutely persistent than the persistent terminals. 
^ Presidential address before The Palaeontological Society, Albany meeting 1916, 
N. Y. State Mus., Bull. 196, 1918 (107-38). 
2 Die Phylogenes Fragestellungen zu ihrer exakten Erforschung. Berlin. Gebr. Born- 
trdger. 1921. 
NEW FORMS OF LIFE FROM THE SILURIAN 
By Rudoi^ph Ruedemann 
State Museum, Albany, N. Y. 
Communicated by J. M. Clarke, January 29, 1922 
The Silurian of New York (Bertie waterlime and Lockport limestone) 
have recently yielded some extraordinary fossils which are now under 
investigation. 
There are algae with well-preserved air-bladders, and primitive land- 
plants with thick coaly tissue. The graptolites, however, are the most 
striking: Dictyonemas, a foot and more in diameter, and varied types of 
the Inocaulis group. The latter possess thickly sheathed, glove-finger 
