the victorian naturalist. 69 



Calcareous Group. 



Order I. — Homoccela, in which no flagellate chambers are 

 present, but the collared cells are confined to the gastral 

 cavity. 



Exs. Leucosolenia stolonifer, L. stipitata and L. 

 pulcherrima. 



Order II. — Heterocosla, in which the collared cells are con- 

 fined to the flagellate chambers. 

 Family I. — The flagellate chambers project freely. 



Ex. Sycon raphanus. 

 Family II. — The flagellate chambers are enclosed by a cortex, 

 (i.) With radiate arrangements of chambers. 



Ex S.ycon gelatinosum. 

 (2.) With chambers scattered irregularly. 

 Ex. Vosmaeropsis macera. 



The names in the above list do not convey any idea of the 

 shape and size of the specimens selected as examples, and it will 

 be well, therefore, to state a few simple facts in regard to their 

 external appearance and habits of growth as aids to discovery 

 and identification, since one specimen gathered and identified is 

 of more practical value than mere theoretical knowledge gained 

 from twenty pages of a museum catalogue. 



The first-named in the list is Leucosolenia stolonifer, and a 

 more useful sponge can scarcely be found for our first study, 

 because of its extreme simplicity of form and structure. We are 

 fortunate in having so simple a sponge so close at home. It 

 consists of a colony of three or four very thin walled tubes 

 springing vertically from a slender rootlike bar of sponge tissue 

 running horizontally along the surface of the weed to which the 

 colony is attached by down-growing processes. Each tube reaches 

 a height of about i^ inches, having a thickness of ^-inch. At 

 the very top of the tube is the osculum for the outgoing stream 

 of water. A thin section across one of the tubes shows an 

 extremely thin wall pierced by pores which communicate directly, 

 by means of narrow canals, with the central cavity which alone 

 is lined by collared cells. The existence of the simplest possible 

 canal-system and the absence of flagellate chambers render this 

 sponge specially acceptable to a novice in spongology. There is 

 little to learn about it, but this little must be learned before any 

 real progress can be made with the anatomy of the more 

 complicated forms. The sponge, unfortunately, is not of common 

 occurrence, only one specimen, creamy white in colour, being 

 captured during the visit ; and that one was found attached to a 

 piece of seaweed floating in with the incoming tide. 



Closely allied, in relationship, to L. stolonifer, but differing en- 

 tirely from it in appearance, is L. stipitata, found in considerable 



