IN SPONGILLA FLUVIATILIS. 57 



as it does from the broad base of the lining boarding of the Lock, 

 its growth is regular and symmetrical, as shown in its network. 

 In a vertical section this is well demonstrated, and we find that 

 nearly all the spicules thus seen are spinous, the spines being well 

 developed. But if we get a horizontal section this is somewhat 

 reversed, and the smooth spicule is then predominant ; and when we 

 give a closer examination into these constituent elements, it is found 

 that there is about an equal division as regards numbers, and that 

 half the spicules are spinous, and half smooth ; the latter generally 

 a little longer. As regards the birotulate spicule of the ovarium, it 

 is in all respects similar to that of Teddington (fig. 2). 



Let us now retrace our steps, and row back through that pretty 

 part of our beautiful river, from Hampton to Surbiton ; a trip at 

 all times enjoyable, not even wanting the good excuse of the 

 naturalist. Here, by the little eylet occupied by Messenger's Boat- 

 house, &c, both our native Spongillas are found in abundance. They 

 grow on the moored barge-house, beneath the floating baths, and all 

 round the wharf-boarding, in various stages of development. But 

 the specimen to which I draw attention was attached to the floating 

 barge, on the side towards the island, between which and it was but 

 a small interval shaded from light. And, close by its side also grew 

 S. lacustris, overlapping it in places ; and so much alike, in every 

 external character, that, without a lens, no distinction could be 

 made between them ; the branching form of the latter being wanting. 

 It was a rebuke to naturalists in its name, so untrue as the Lake 

 Spongilla, when flourishing under precisely the same conditions as 

 S. Jiuviatilis, but also assuming its shape ; showing, that their 

 law, at least, must not be like that of the Medes and Persians, 

 which altereth not. 



The first point which close observation brings to notice, is, that 

 the hisjnd character, which generally marks this Spongilla, was 

 wanting ; but, in place, was a felting of spicules on the dermal 

 surface. It is a condition not hitherto observed. More intimate 

 knowledge obtained by sections and close examination of the spicules 

 reveal the fact of a still greater development of the spinous charac- 

 ter, as the smooth type has all but vanished, leaving only here and 

 there a representative. As regards the birotulate form there is no 

 change, as it conforms to the two last (fig. 3). 



So, here then, we have travelled the circle ; beginning with the 

 smooth spicule of the type, we end by finding it yield place to the 



