S. W. Ford—Additional Embryonic Forms of Trilobites. 259 
suggest for them a genetic kinship (see Hicks, Quart. Jour. 
Geol. Soc., vol. xxviii, pl. 7, figs. 1-11). Salter states that, in 
the British Primordial, the genera Paradoxides, Anopolenus and 
Olenus follow each other in regular order—first Paradoxides, 
then Anopolenus and lastly Olenus; and in America we appear 
to have a like succession—first Paradowxides, then Olenelius, and 
lastly the Olenoid types of the western States. 
The remarkable intersection of differential characters observed 
in the embryonic forms of Olenellus asaphoides, and the trans- 
formations there noted, appear to me to point to the Embryo as 
the principal theatre of organic evolution in general; and they 
strongly suggest, to my mind, the operation of profounder laws 
than any, hitherto assumed, as having effectively directed its 
co It seems well-nigh absurd to ascribe such effects to 
natural selection, or the influence of environmental conditions, 
although such influences have, no doubt, to some extent, modi- 
fied the total result. So far, however, as we are enabled to 
judge, the conditions of existence in Primordial times were 
June 13th, 1881. 
