424 Prof. E. Hack el on the Calcispongia^ 



species ; B. 1 genus with 3 species ; C. 3 genera with 21 

 species ; D. 21 genera with 111 species ; E. 43 genera with 

 181 species ; F. 43 genera with 289 species. On the other 

 hand the artificial system might experience the following six 

 arrangements : — G. 1 genus with 7 species ; H. 2 genera with 

 19 species ; I. 7 genera with 39 species ; K. 19 genera with 

 181 species; L. 39 genera with 289 species ; M. 113 genera 

 with 591 species. Every one of these twelve systems might 

 cite in its support arguments such as every systematist brings 

 forward in favour of his subjective conception. None of them, 

 however, could ever be demonstrated as the absolutely true 

 system. This circumstance shows most clearly that no absolute 

 species exists, and that species and variety cannot be sharply 

 separated *. 



3. Generic and Sjyecific^ Connective and Transitory Varieties. 



The different forms which I have cited in the system of the 



Calcispongiae as generic and specific, connective and transitory 



* Tile twelve systems here cited as examples (in whicb, moreover, the 

 external form is not taken into consideration) would he as follows : — 



A. I, Natural system with the widest conception of the idea of species 

 (in the first degree) : a single genus with one species, Calcisponyia 

 yrantia. 



B. II. Natural system with a very wide extension of the idea of species 

 (in the second degree) : a single genus with three species: 1, Calcisponyia 

 ascon, 2. C. leucon, 3. C sycon. 



C. III. Natural system with a naiTower conception of the idea of species 

 (in the third degree) : 3 genera (Ascon, Leiicmi, Sycon) with 21 species. 

 Here the 21 groups of forms which the next system accepts as genera 

 {Ascctta, Leiuefta, Sycetta, &c.) are reckoned as species. 



D. IV. Natural system -wnth average extension of the idea of species 

 (in the fourth degi-ee) : three families (Ascones, Leucoties, Sycones) with 

 21 genera and 111 species. 



E. V. Natural system with a narrower extension of the idea of species 

 (in the fifth degi-ee) : 3 families with 43 genera and 181 species. This 

 system is attained when the subgenera cited in the natural system in the 

 second volume are accepted as '' good genera," and the " specific varieties" 

 or incipient species as " good species." Their characters are sufficiently 

 sharply marked and relatively constant. 



F. VI. Natural system with a very narrow extension of the idea of 

 species (in the sixth degree) : 3 orders, with 21 families, 43 genera, and 

 289 species. This system is attained by a further analytical specification 

 of the fifth system, the " generic varieties " of the latter being raised to the 

 value of distinct species. 



G. VII. Artificial system with the widest conception of the idea of 

 species (in the first degi-ee) : aU Calcispongife form a single genus, Grantia 

 (Fleming, 1828), or Leucalta (Grant, 1829), ox Calcisponyia (Blainville, 

 1834). We may then distinguish the following as seven species : — 

 1. Calcisponyia doroyrantia ; 2. C. eystoyrantia ; .3. C. cormoyrantia ; 4. C. 

 ccBiinyrantia ; 5. C. tarroyrantia ; 6. C. cophnyrantia ; 7. C. metroyraivtia. 



