OYSTER BOTTOMS IN MATAGORDA BAY. 67 



through the external pores. Although so far as the writer is aware 

 no investigations Jiave been made, it undoubtedly feeds upon many 

 of the same organisms that constitute the oyster's food, but so small 

 must be the quantity required that it can not have much effect in de- 

 priving the oyster. The only real damage done by this organism is 

 the gradual disintegration of the old shells to the lessening of their 

 value as cultch and the occasional weakening of the shells of living 

 oysters so that they break in culling. 



Boring sponge {Cliona sulphur 'ea) . — This animal, like the preced- 

 ing, attacks the shell rather than the oyster itself. It apparently is 

 not so troublesome in Matagorda Bay as on some other portions of 

 the coast, but evidence of its work was found on certain of the reefs 

 below Dog Island; above that place the water is generally too fresh 

 for it to grow in profusion. It produces what are generally known 

 to the oystermen as " worm-eaten " shells, a condition characterized 

 by a network of small irregular burrows which often so completely 

 fill the shell and leave so little solid material that it can be crumbled 

 in the fingers. In its young stage the sponge fills these galleries w T ith 

 a yellow pulpy mass and projects from the external orifices in little 

 mushroom-shaped papilli or pimples. In its older stage it forms a 

 large sulphur yellow or pale orange mass wdiich ma} 7 completely 

 embrace the shell in which it originally grew\ The means by which 

 it burrows has not been definitely determined, but it probably exudes 

 a fluid having a solvent action on the limy material of the shell. 



The boring sponge damages the reefs in several ways. It breaks 

 up the shells and covers them with a slimy deposit, both of which 

 processes tend to unfit them for the attachment of future growths of 

 oysters. It renders the shells fragile and difficult to cull, besides 

 making the oysters unattractive as shell stock, both on account of 

 their exterior appearance and the mottled and discolored aspect of 

 their interior. It serves to encourage the accumulation of other 

 debris on the beds. And, finally, as the galleries frequently pene- 

 trate the inner face of the shell, the oyster to stop the gaps is forced 

 to lay down successive deposits of shell and apparently suffers more 

 or less damage, for almost invariably badly infested individuals are 

 poor in quality. 



Barnacles (Balanus). — Barnacles are generally a minor or insig- 

 nificant enemy to the oyster. Their effect is very much the same as 

 that produced by the mussel, their rapid growth tending to produce 

 crowding in the oyster clusters, besides making the shells unattract- 

 ive and uncomfortable to handle. In Matagorda Bay they are not 

 especially troublesome, though found in small numbers on a consid- 

 erable number of the beds. 



"Red grass.-'' — The growth locally known by this name is not a 



