2i6 The American Geologist. October, lot.i. 
thousands of feet, and in similar zones the separation of dif- 
ferent beds is ahnost as great, yet the biological expression 
is not extremely contrasted throughout and, as the French 
translator of Matthew's paper has remarked* (Soc. Mai. de 
Belgique ; Ann. 4th, 1888, p. 552). the lowest beds holding 
the earliest trilobites ofifer no significant evidence, in their 
trilobitic remains, of embryonic or formless stages of de- 
velopment. That is while larval conditions may appear they 
are stages in an individual life history, not fixed preparative 
stages in the development of a phylum.* It is logical, or at 
any rate natural to assume that throughout the long periods 
of time antecedent to the Cambrian age these preparative 
stages were evolved and completed, but as a matter of con- 
temporaneous geological history they have not yet been dis- 
covered, and possibly, from their perishable nature, cannot 
be. The trilobites of .the Cambrian in their numerical abund- 
ance, their very considerable specific variation, their sudden 
appearance in the paleontological series, and their apparent 
chronological isolation justify the characterization of a bi- 
ological crisis. Tl:e only wa}' to throw light upon this prob- 
lem is to consider the circumstances of similar biological 
multiplications and intensity in living faunas. 
It would seem certain that the trilobites enjoyed an al- 
most complete immunity from those accidents which today 
devastate the young broods of crustaceans, while the almost 
infinite resources of multiplication with which this phylum is 
endowed permitted unrivalled opportunity for propaga- 
tion and distribution. Profs. Sars and Boeck have 
pointed out the numerous dangers to which the young lobster 
is exposed and which must necessarily greatly reduce the 
total numerical maximum attainable by that animal. The 
young larval lobster suffers from the attack of fish, the en- 
tangling effect of sea- weed, the injurious physical character 
of the coast, whither currents may transport them, sudden 
changes of temperature, y and impaired vitality from abrupt 
or delayed discharge from the parent. 
* There can be of course, no demurrer to the conclusion that many genera 
of Cambrian trilobites, perhaps the more common and generallj' noted, repre- 
sent protaspic stages in more advanced and later evolved genera, btit as found 
they are mature defined and individualized genera. Dr. Beecher has indeed said 
that the Opisthoparia (Conocoryphidae, Olenidae, Asaphidae Lichadidae, etc.) 
probablj' culminated during the Cambrian. 
f Although in 1879 lobsters with roe were successfully transported to the 
■west coast and "had with them over a million eggs nearly ready to hatch," 
yet no rcsitlts have apparently flowed from the experiment. 
