PROCEEDINGS OF SOCIETIES. 193 



(2.) Clionidae — the perforating sponges ; they use their spicula 

 for perforating ; each species makes a pattern of its own like 

 the leaf-burrowing caterpillars. Silurian species have been 

 observed. (3.) Spongidoi — having the structure of Spongilla. 

 Fritz Miiller has lately described (see Quart. Chronicle, vol. 

 for 1866) a genus Darwinella, Avhich has horny spicula as 

 well as horny fibi'cs building up its skeleton. Some sponges 

 have very few spicula, and are then used for washing, &c. 

 Grantia has calcareous spicula, which are very long, and 

 placed round the apertures. They are the nearest approach 

 to the enormously long siliceous spicula of Hyalonema from 

 Japan. Professor Huxley fully supported Max Schultze's 

 view of the parasitic nature of the Actinozoon found at 

 the base of Hyalonema. (4.) Petrospongidm — abound in the 

 chalk : such forms as Ventriculites, &c. They have a peculiar 

 arrangement of the fibres of their skeleton (fig. 2) . They are 

 doubtfully placed among the sponges. (5.) Tethyada — large 

 spheroid bodies with huge spicula radiating from the centre; 

 sometimes provided with anchors at their ends. Their sexual 

 condition has been well studied. 



Lecture IV. — The Infusoria seem to stand between Pro- 

 tozoa and Annuloida. ParamfBcium was described as in 

 former lectures, as a type. (See Lect. on Classif., 1865.) 

 A distinct cuticula was admitted for the Infusoria, which is 

 co7itinuous with the cilia. The mouth leading into the semi- 

 liquid substance of the body, and the appearance of pellets of 

 food surrounded by water when taken in, were described. 

 Professor Ehrenberg still retains his view as to j)lurality of 

 stomachs {Polygastrica), being ^^a man who does not give 

 up an opinion which he has once adopted.'" The cause of 

 the slow rotation of the food within Infusoria is still un- 

 known. Professor Huxley compared it to the circulation in 

 Anacharis and Valisneria. A distinct anal aperture is now 

 admitted to exist in Infusoria, which can only be detected 

 when matter is being expelled from it. The chlorophyl 

 granules which abound in some Infusoria are admitted by 

 Professor Huxley to be formed in all probability by the 

 animal itself. He also adopts the view that the contractile 

 vesicles have a permanent communication with the exterior. 

 The notion that Infusoria are unicellular organisms has had 

 to be considerably modified. Their so-called nucleus is only 

 in a limited sense to be regarded as a nucleus ; it is in 

 another sense an ovary. Miiller, Claparede, Balbiani, and 

 lastly. Stein, in his second great book lately published, have 

 contributed to our knowledge of sexual reproduction in 

 Infusoria. Balbiani showed that what Miiller took to be a 



