THE MONAXONID^. 



327 



fact that the three additional rays are given off from the hinder (proximal) end of the shaft and 

 not from the anterior (distal). 



By Oscar Schmidt this sub-order is divided into the five following families : 



Orders, Carter. 



Holorhaphidota. 



I-}/ > Hies, O.S. 

 Kenierinas 

 Desmacidinte 

 Suberitidirue 

 Ch-.ilinopsidime 

 Chalineaj 



Eehinonemata (pars) 

 Khaphidonemata. 



Carter's classification of these Sponges is shown in the table. 



In the Renierinse* the chief spicules are usually bi-radiate (acerate), and are generally collected 

 to form fibre, in which they are arranged like the elongated cells in the woody fibre of plants. 

 Spongin may develop about this fibre, cementing the spicules together, and then the Renierine 

 becomes a Chalinine Sponge, but so easy is the transition between these families that Carter makes 

 mention of a Sponge which is Renierine or Chalinine, according to the locality in which it is found. 

 The Renierinse are among the commonest of Sponges, 

 and are well represented on the British coasts ; the 

 hardy Amorphina panicea, or "Crumb of Bread" Sponge 

 (Fig. 3), found at most watering-places, is a good example. 

 It grows in thick crusts, of a plant-green colour, rising 

 into little conical volcano-like elevations, which open by 

 an oscule at the summit ; pores occur in the skin over the 

 interspaces of a very regular spiculous network which 

 lies beneath. Its spicules are simple acerates, sharply 

 pointed at each end, and crowded loosely together into Fig. 14. STATOBLASTS OF SPONGILLA. 



irulp finite fiViro wl->ir>li fnvme on aHrKWvfhpT- irvfrml-ar TIP+- A - Statublast of S.flnvMilis, in its natural state, x 50; B, of & 



unite note, wnicn lorms an aitogetne icguiar net- facw, alter treatment with nitric acw,xd 



work in the body of the Sponge. From this loose texture, 



and the fact that owing to the absence of spongin, the Sponge readily crumbles between the finger-s 

 when dry, it derives its name of " Crumb of Bread " Sponge. 



Another common example is the Spongi lla fluviatilis of our rivers. It occurs in irregular masses 

 of much the same colour as A. panicea, with which it closely agrees in general structure ; it differs, 

 however, in common with the sub-family Spongillina, to which it belongs, both from that and all other 

 Sponges, in the fact that it reproduces itself not only by ova, but by curious little bodies (Fig. 14) 

 known as winter-eggs, or statoblasts, which somewhat resemble the statoblasts of the Polyzoa. Their 

 history has been the subject of a classic memoir by Carter, who finds that they originate near the base 

 of the Sponge, by certain cells congregating together and becoming surrounded, except at one point, 

 by a spherical shell, a pin's-head in size, of complicated structure, its external layer consisting of 

 spicules of singular form, like a pair of wheels on an axle in miniature. The axle lies radiately in 

 the wall. The spot where no shell is formed remains as an aperture, through which in spring, 

 the amoebiform contents creep out from their winter quarters, and soon develop into the young 

 Sponge. 



The various members of the sub-family Spongillina do not differ except in trifling details from 

 SpongiUa; though they have not yet been described from Australia, they are otherwise of world-wide 

 distribution, and from this we may infer that they are a group of great antiquity. Owing to the 

 rarity of fresh-water fossils, and the exceptional preservation of Sponge remains, it is not to be 

 expected that we should find direct evidence of this, and it is, therefore, all the more satisfactory that 

 traces of SpongiUa have been found so far back as the Purbeck strata, where its chief spicules have 

 lately been detected in fresh-water chert, 



SpongiUa is so similar in many respects to Amorphina, which sometimes lives in brackish water, 

 that it is very possibly derived from it. It is a singular fact that of the many hundreds of widely 

 different kinds of Sponge, none but a small rigidly-defined group should be found inhabiting inland 

 waters. This is probably due not to the inability of Sponges to adapt themselves to fresh water, but 

 rather to the fact that they are propagated by ciliated larvse, which drift about at the mercy of 



* After the naturalist Eenier. 



