NO ABSOLUTE SPECIES EXISTS. 95 



observations, by measurements, by drawings, by facts and 

 inferences, had produced evidence, which acute opponents 

 of the immutability of species had not brought forward 

 before me, that in these sponges, species and genera, and 

 consequently fixed systematic unities in general, had no 

 existence. The other division of the same class, the cal- 

 careous sponges, had been treated with unrivalled mas- 

 tery by Haeckel in his Monograph.^^ 



He was able not only to confirm my statements, but, 

 owing to the smaller compass and the greater facility 

 of observing the group selected for study, to advance 

 with more sequence and continuity from the observation 

 of details to the whole, to portray its morphology, 

 physiology, and evolutionary history with the utmost 

 completeness. He then challenged the obstructive 

 party with the assertion that, according to subjective 

 opinion, either one or 591 species of calcareous sponges 

 might be accepted, but " that no absolute species exists, 

 and that species and varieties cannot be sharply sepa- 

 rated." Whoever after these demonstrations cleaves to 

 the phantom of species, without either proving thatvthe 

 facts have been falsely observed, or that they may be 

 interpreted otherwise than in favour of the stability of 

 species, — whoever, as Agassiz has recently done, ignor- 

 ing any such researches, publicly asseverates that in no 

 single case has the mutability of any species been ex- 

 hibited,— rscarcely preserves the right to participate in 

 the great controversy by which Natural Science is now 

 perturbed. 



There is, however, as we have already mentioned, a 

 second direction in which the mobility of " species " must 

 be demonstrated, not the direction of breadth, but of 



