24 On the Relationship of the Sponges to the Corals. 



were some " microscopically small, but yet perfectly developed 

 {i. e. ovigerous) " ones, " in which there are actually no traces 

 of cutaneous pores " (and no spicules ; at least none are men- 

 tioned in the " classification "). The entire body consisted of 

 an "elongate rounded sac (stomach), with a single opening 

 (mouth) on that extremity of the body which is opposite to 

 the point of attachment." For this sponge Hackel has pro- 

 posed the name of Prosycum. Indeed this is the starting- 

 point or base of his Classification of the Calcispongise ; and, 

 of course, the absence of cutaneous pores makes its cavity a 

 stomachj for there is no evidence of any other means by which 

 nourishment could be obtained. 



But is this not slender evidence to go upon, viz. the exami- 

 nation of a microscopic object preserved in spirit? If exa- 

 mined in the living state, might it not, like the young Spon- 

 gilla (for it could hardly be much smaller) have possessed 

 amoeboid sponge-cells which might have enclosed particles of 

 food on the outside of the sac, and discharged the ingesta into 

 the so-called stomach, just as in Clathrina sulphur ea^ where 

 the walls of the tubular structure are so thin that its areolar 

 structure, beset with sponge-cells, can hardly be distin- 

 guished. 



Of course I allude to these points for the purpose of elicit- 

 ing truth, which no one desires more than Prof. Hackel. 



As regards the development of the so-called ovum, it is 

 stated, at p. 12, that the excretory canal commences " by a 

 small central cavity (stomach)," which " extends, and, break- 

 ing through at one pole of the longitudinal axis, acquires an 

 aperture, the mouth ;" and at p. 114, that the " pores are simple 

 breaches in the parenchyma, which perforate both layers of the 

 body-wall (ectoderm and entoderm)." The first stage repre- 

 sents his Prosycum^ and the second, where the pores are added, 

 his Olynthus. In his Clistolynthus the mouth is closed up 

 " by retromorphosis." Where the mouth is closed, the nou- 

 rishment mustj of course, come through the pores^ and not 

 through the so-called stomach. 



Such are Hackel's views ; and his classification of the Cal- 

 careous Sponges is carried out upon them in extenso. His 

 theory that the vent of the sponge is the mouth, and the large 

 excretory canal the stomach, is the principium et fons of 

 all. 



But how can this be maintained, when it has been proved 

 that the greater part of the Sponge consists of flagellated Rhi- 

 zopoda which take in crude material for nutrition, and probably 

 supply the necessary elements of sexual generation ? 



