376 HYATT: GENEALOGY OF ACHATINELLUXE. 



for many years, and happily succeeded in introducing to the 

 favorable notice of the younger paleontologists of this coun- 

 try. This is founded upon what has 'been falsely called ' ' the 

 Law of Biogenesis' by Haeckel, and in spite of just opposi- 

 tion and well-founded criticism, adopted by a large number 

 of scientific workers. This law was really discovered by von 

 Baer, and completed by Louis Agassiz and Vogt and was 

 simply baptized by Haeckel with an old name already having 

 a fixed and a different meaning in scientific literature.* 



Natural selection might be called upon to account for the 

 brown protective colors of Amastras living on the ground, but 

 the prevalence of brilliant, conspicuous colors in the arboreal 

 species, and the presence of similar brilliant colors in some 

 species that are habitually concealed, and the constant ten- 

 dency to the repetition of similar variations in different 

 species are all at variance with this hypothesis. 



There are also other constant modifications of form that 

 correlate with the general morphology of Gastropoda. The 

 ontogenetic development of a gastropod follows certain gen- 

 eral lines of modification. The protoconch is more or less 

 bag-like, and when the conch is begun it necessarily starts as 

 a tube continued from the aperture of the protoconch. In 

 shells that revolve with the principal axis held continually 

 in the same plane or nearly in the same plane, like Planorbis, 

 two hollows, or nearly equal umbilici, are formed, one on 

 either side of the shell. On the other hand, unequal or 

 asymmetrical spirals are formed by excessive growth to one 

 side which necessarily elevates the opposite side into the apex 

 of a spire, and generally obliterates the umbilical 'cavity. 

 Sometimes this remains for a time, but in most gastropods it 

 may be said to be a lost character. Nevertheless in the most 

 acutely spiral shells, as a rule, the earliest stages of the conch 

 are less asymmetrical than the subsequent states. 



In other words, the ontogeny shows that the primitive form 



* Abiogenesis was originally used for spontaneous generation of life 

 from inorganic matter and " biogenesis " for the theory that life was 

 continuous and that organisms could originate or be generated only 

 from life. 



