THE ATTACHMENT OF OYSTER LARV.E. 147 



KVIlo-g, '99, showed the importance of the foot in aiding the 

 larva <>f Mya to obtain attachment. Sigerfoos, '07, noted that 

 larval shipworms possess a powerful foot by means of which they 



p rapidly over surfaces and select spots favorable for fixation 

 to the exclusion of those which are not suitable. Field, '09, 



es that the larvae of .}fytilits creep from unfavorable situa- 

 tions upon seaweeds to locations which are better adapted to 

 them. Belding, '10, describes the foot of the larval Pecten, a 

 most important organ, since it is used for swimming as well as in 

 crawling. Brlding, '12, showed that in the full-grown larva of 

 Venus the foot likewise is used in swimming as well as for crawling, 

 and for procuring attachment. 



Tli.it the use of the foot enables oyster larvae to exercise sonu- 

 M-K-ction in seeking a place of attachment is evident from the 

 \\idr <lillrrenres in the number of spat procured when \.uioii- 

 kinds of cultch are placed together in the water. I h.i\ e n cntly 

 shown (Nelson, '23,) that oyster larva; will not attach to >ln-!U 

 \\hich are extensively pitted by the boring sponge, Clione, or 

 \\hiili are badly corroded and which present suit.ni-, ih.it an- 

 nit i iscopically rough. 



For some hours before oyster larva.- set they may In- oli-rrved 

 iiio\ing about over various surfaces with the \rluin e\ten<led, its 

 cilia beating actively; and with the foot protruded .unl ln-nt at 

 right angles, thus bringing the distal half in contact with the 

 Mil 'stratum. The foot remains quiescent in this portion while 

 the larva slowly "skates" along, as it \\i-n-, pn-prllrd by the 

 velum, but aided somewhat by the cili.t on the looi. Thru, 

 swimming upwards, the larva progresses a short dist.inci- thnm-li 

 the water and drops down to the Milisir.itnm to coniiniu- as 

 before. In this manner the larva m.iy w.nult -r over .^n .qpr'ci- 

 able area before it eventually attaches i Nelson, '21 \ 



In this connection it is well to correct tin- idr.t ln-l<l \>\ \ -ter 

 growers and by some scientists also, that attachment of tin- 

 oyster larva occurs when its shell becomes so he.ivy that the 

 animal sinks to the bottom, unable longer to -\\ im. 1'or e\ani|)U-, 

 Stafford ('13, 34) says: "when presumably the lai\.r bcconu- 

 too hea\y to swim with ease, settle towards the bottom, creep 

 about, and select some clean solid surface upon which they fix 

 themselves. 1 



