332 B. F. KINGSBURY 



Karl Peter ('lOj critically examines the biogenetic law and 

 seems to reject it. He explains the development and persistence 

 of the branchial pouches as due to the middle ear and the ductless 

 glands that develop out of them, but in Lacerta, which he chooses 

 as an example, he is compelled to confess that this point of 

 view hardly suffices as an explanation of the development of 

 the fourth pouch, fifth pouch, and the sixth pouch (his inter- 

 pretation) on one side. Kranichfeld ('14) looks at the problem 

 in a different w^ay. His contention is that the embryonic pharynx 

 is not a 'vestigial' structure but possesses throughout a function 

 correlated with the embryo's nutrition (metabolism) and hence 

 it is but to be expected that glands having important metabolic 

 functions should develop from it since their function is but a 

 continuation of a primary one possessed by the entire pharyngeal 

 epithelium. These criticisms do not seem to me to weaken the 

 general vaHdit}^ of the biogenetic law but rather to strengthen 

 it, inasmuch as the}^ must of very necessity concede that the 

 JDharyngeal pouches, clefts and arches, do exist and are homo- 

 logous with the gill pouches, clefts and arches of lower forms. 

 It becomes possibly a matter of definition, as is so often the case. 

 If interpreted to mean that there are in the development of the 

 individual definite stages corresponding to definite ancestral 

 type forms, the 'law' does not of course hold (Keibel '98); 

 but as the formulation of a fundamental element in the mor- 

 l^hological pattern of development, which is only comprehensible 

 in the light of descent, the biogenetic law cannot be escaped. 

 It is, I believe, but a special aspect of a more fundamental 

 principle of life processes, correlated with their cyclical char- 

 acter and including 'heredity,' which may be designated some- 

 what loosely and metaphorically perhaps as the 'Principle of 

 ancestral resemblance.' It is not the intention to enter into 

 a detailed discussion of the 'biogenetic law,' but as to disappoint- 

 ment that the biogenetic law has not afforded much in the way 

 of explanation of biological facts, it may be stated that it stands 

 for fact and is itself subject to explanation. 



The fact remains that the morphology of a large part of the 

 face and neck are comprehensible only on a clear comprehension 



