[ 837 ] 



^be Spongiba or porifera. 



By R. Lawton Roberts, M.D., and Miss Florence Phillips. 



Plates XIV., XV., and XVI. 



INCE the time of Aristotle, the sponges have been 

 regarded as interesting objects of enquiry, but 

 during the present century they have proved a 

 fertile source of discussion, of warm controversy, 

 and of laborious investigation on the part of skilled 



(;*-m^i biologists. 



^i 'f^j^ Formerly, the point at issue was whether the 



^"fv^-^ Spongida were of the nature of plants or animals, 

 or whether or not they constituted a connecting 

 link between the vegetable and animal kingdoms. Latterly, since 

 it was shown by Grant that Sponges possessed animal character- 

 istics, the greatest differences of opinion have arisen as to the 

 exact position occupied by them in the scale of animal life. 



Many competent observers insist that the Sponges are closely 

 allied to the Protozoa, minute and lowly animal forms, composed 

 of homogeneous or somewhat granular, gelatinous substance or 

 sarcode, devoid of any true organs or any proper cellular tissue, 

 and in some instances possessing cilia, flagella, or tentacula. As 

 typical of this side of the question, the view expressed by H. 

 James Clark in 1868 may be mentioned, that the Sponges "must 

 be regarded as compound colonial forms " of Flagellate Infusoria. 

 Quite an opposite theory was advanced, in 1869, with great 

 ingenuity and forcible argument, by Ernst Haeckel. This autho- 

 rity urged that the association of the Sponges with the Protozoa 

 was an error ; that, on the contrary, the Sponges were of a higher 

 grade, being properly allied to the Corals and Zoophytes, or Cce- 

 lenterata. He insisted strongly that the canals which permeate 

 the Spongida, were comparable with the digestive-circulatory 

 cavities of the Corals, that the spaces, immediately including the 

 larger orifices (or " oscular area " ) of a sponge, represented indi- 

 vidual Polypes, and that the reproduction of the Sponges was 

 effected, as in the Corals, by means of ciliated larvae (or ''gastruW), 



International Journal of Microscopy and Natural Science. 



Third Series. Vol. III. y 



