426 Prof. E. Hackel on the Calcispongise 



Leucetta primigenia represents seven different genera of the 

 artificial system ; and Sycandra compressa furnishes the arti- 

 ficial system with no fewer than nine distinct genera. 



2. The specific varieties of the natural system are incipient 

 species of the natural system in the sense of the theory of de- 

 scendence. By further development and increasing constancy 

 of the characters by which the specific varieties of a natural 

 species are distinguished they would raise themselves to the 

 rank of ''^ bonce species^ An analytical system that takes a 

 very narrow conception of the idea of species might already 

 recognize them as species. Thus, for exam})le : Ascandra 

 variabilis would divide into four natural species [A. cervi- 

 cornisj confervicola, arachnoides, and hispidissima) ; Leucetta 

 primigenia would form three good species {L. isor-aphis, micro- 

 raphis, and megaraphis) ; and Sycandra compressa would even 

 break up into six natural species {S. fbliacea, ^^e^i/ii'^era, 

 clavigera, rhopalodes^ lobata^ and poly m07plia). Many of these 

 specific varieties have, in fact, already been described as 

 species. 



3. The connective varieties of the natural system are direct 

 transition forms between the genera of the natural system. The 

 foundations of a new natural genus are laid by very trifling 

 changes in the constitution of the skeleton. Thus, when certain 

 triradiate spicules of the skeleton of Ascetta {Leucetta or 

 /S'j/ce^to) , which is composed only of triradiate spicules, develop 

 a fourth ray, this genus passes into Ascaltis {Leucaltis or Sy- 

 caltis). For example : — Ascandra variabilis furnishes trans- 

 ition forms to four natural genera [Ascaltis^ Ascortis, Ascu- 

 linits, Ascyssa) ; Leucetta primigenia produces connective forms 

 towards three genera of the natural system {Leucaltis^ Leucortisj 

 Leucandra) ; and Sycandra compressa passes into Sycortis. 



4. The transitory varieties of the natural system are direct 

 transition forms betiveen the sjiecies of the natural system. They 

 are the "transitions from one good species to another" which 

 horrify the opponents of the theory of descendence. Such in- 

 termediate forms, the existence of which is denied by dogmatic 

 species-makers, occur in abundance among the Calcispongite. 

 Thus we have transitions from Ascandra variabilis to A.pinus, 

 A. Lieberkiihiiii, a,nd A. complicata'^ transitory intermediate 

 forms between Leucetta primigenia and L. pandora and 

 sagittata ; and direct transitions from Sycandra compressa to 

 S. utriculus and lingua. 



4. Polymorphosis and Polymorphism. 

 One of the most remarkable peculiarities of the Calcispongise, 



