87 



process by which animals are produced. The idea of the introduc- 

 tion of many individuals of a species without parentage is common to 

 both theories. Of the nature of the process, or even of the existence 

 of any process more than the volition of the Divine Mind, we have 

 however no conception." The theory of the manifold origin of species 

 approximates more nearly to that of spontaneous generation, if we 

 do not admit, as does Professor Agassiz, the contemporaneous intro- 

 duction of the original individuals. Of course the doctrine of con- 

 temporaneous origin must have a geological latitude. But wheth- 

 er in any sense it can be admitted, must be determined by the geolog- 

 ical history of species. If the subtypes of those species, whose lon- 

 gevity is sufficient to furnish opportunity for observation, have been 

 gradually introduced, the theory of contemporaneous origin cannot be 

 applied to species, any more than to genera, except so far as results, 

 with a mathematical necessity, from the circumstance that they are less 

 comprehensive groups. 



It is obvious that an illustration of this subject may be found in 

 the different species and varieties of mankind.* 



Description of a new genus of IIelicidae, from Jamaica. By C. 

 B. Adams. March 1S50. 



SPIRAXIS. G. t. parva, turrita : columella medio in laminam 

 spiralem producta : apertura ovali, medio partim divisa : labro 

 simplice. 



Shell small and thin, much elongated : with the columella produc- 

 ed into a lai'ge stout spiral lamina, which gradually becomes obsolete 

 in ascending two to four whorls above the aperture : the aperture is 

 oval, but by the contraction of the labrum and the intrusion of the 

 columellar lamina is often divided into the form of the figure 8 : the 

 labrum is simple and indented by a stricture on the middle of the 

 whorl. To this genus may be deferred Achatina inusitata Ad. p. 26 



*In this case all the arguments, which «ome philologists urge against the theo- 

 x\ of the plural origin of the nations which speak affiliated languages, are hased 

 on the assumption that original individuals couUl not have had the same nor even 

 similar languages. Why it should be assumed that unity of Zoological origin is 

 a necessary inference from philogicat athliation or unity, we are unable to con- 

 ceive, it seems to us a perfect example of a noa-seciuitur. 



