410 General Biology 



between our own time and the time when the prototypes of these recent 

 fossils lived, and examples of so-called older forms (those which lie 

 above the recent forms) can be considered evidence for this statement, 

 (d) Those who insist on experimental evidence which is always 

 under the control of the experimenter, say that fossil-remains furnish us 

 only with "descriptions" of what is found. It is a "dead" account. It 

 can never give us an explanation. Explanation and interpretation can 

 only come through our logic. Paleontological evidence is, therefore, all 

 logical and not experimental. A strictly scientific explanation from the 

 experimentalist's point of view must also present experimental evidence. 

 This has not been, and cannot be, done in paleontology. 



2. Genetics. 



Inherited changes can always be referred back to ancient Mendelian 

 recessives meeting, and thus producing a "past" type. No strictly "new" 

 types can ever be formed because the chromosomes never die (so long 

 as there are living offspring), and all that ever happens is that some 

 part of them is thrown out. But, from Avhat is known of Biology, it is 

 impossible to add anything to the offspring which is not already present 

 in the chromosome content of the germ cells. 



3. Comparative Anatomy. 



Similarity of structure by no means proves relationship, as shown 

 by examples of convergent evolution, where tv/o quite dissimilar struc- 

 tures come to look alike in various aspects, due to similar functioning. 

 Witness such experiments as Carey's in which bladder-muscle was con- 

 verted into beating heart-muscle by causing the bladder to simulate 

 heart-conditions. 



The argument from comparative anatomy holds good only if one 

 accept the dictum that "structure determines function," while the experi- 

 ment just mentioned shows that function determines structure, once one 

 has the material with which to work. 



4. Comparative Embryology. 



(a) Any organ not used is likely to degenerate. This accounts for 

 Sacculina degenerating when it assumed a parasitic habit where it no 

 longer uses the various organs it once used. This is not remarkable, 

 and if it proves anything, it proves only that an organism can lose 

 something it once possessed, though it by no means proves that what 

 we have been considering a more complex organism, can arise from one 

 that is less complex. 



(b) The so-called gill-pouches demonstrate only as in (c) that 

 vertebrate forms pass through similar stages of growth and not that 

 one springs from the other. 



