Prionodesmacea 541 



and related species and is applicable to virtually all free-swimming, 

 shelled molluscan forms. 



In determining the most favorable culture medium for the larvae of 

 any particular species of lamellibranchs, consideration should be given 

 to the natural environmental conditions under which its prolific repro- 

 duction occurs. The species mentioned thrive in inshore coastal waters 

 where certain factors such as salinity, temperature, pH, oxygen content, 

 etc., have been found, within a certain range, to be favorable for their 

 development. It is recommended that the seawater used for culture of 

 these larvae conform to the following conditions, — salinity 10 to 28 per 

 mille (1% to 2.8% salt), temperature 20 to 30 C, pH 7.8 to 8.2, 

 oxygen 80% to 100% saturation. If the water supply is obtained from 

 a suitable location and renewed frequently little attention need be paid 

 to variations in these factors within the range indicated. Though the 

 water may be pumped at any stage of tide, that obtained during the 

 low water period has been found to be more suitable for larval growth 

 and metamorphosis. The equipment used for pumping and storage of 

 seawater should be constructed preferably from rubber, glass, or wood, 

 though cast iron and lead lined material is fairly satisfactory when used 

 with large volumes of water. Bronze or other copper alloys should be 

 avoided. 



For detailed studies of the larger and full grown larvae they may be 

 immobilized on a glass slide by the method recently devised by the 

 author, which is as follows: The larvae are removed from solution with 

 a fine pipette, placed to one side of the slide and all excess water drained 

 away with a small camel's hair brush. A drop of marine glue is placed 

 in the center of the slide and allowed to evaporate for a minute or so 

 until a thin sticky film has been formed. The larvae are then picked up 

 with the tip of the brush, gently placed in the glue in the desired position 

 and the slide transferred to seawater about five minutes later, after the 

 glue has set. The larvae may be immobilized by either valve and should 

 be placed with the hinge line parallel to the surface of the slide so as not 

 to interfere with shell movements and normal functioning of the velum. 

 This method has greatly facilitated studies of the anatomy, behavior, 

 and reactions of oyster larvae and may be used equally well with 

 related forms. Larvae of Mytilus, Mya, Teredo, and Ostrea that were 

 immobilized in this manner appeared to grow and develop normally and 

 were protected from possible injury by placing the slides in shallow, 

 rectangular staining dishes. 



The final procedure in rearing larvae is to carry them through the 

 setting or spatting period during which they either settle to the bottom 

 or attach to submerged objects and then undergo a rapid metamorphosis 

 that is followed by gradual modifications in morphology to that of the 



