200 Phylum Annelida 



the diatoms of the ocean here at our laboratory. In addition to this 

 another culture was sent to me by Dr. S. C. Brooks a year ago from 

 Woods Hole. Of these cultures the most suitable for food for growing 

 larvae are the first and third, as these are small in size and stay in sus- 

 pension. 



FEEDING 



Because it is impracticable to know the concentration of the diatoms 

 within any culture, and because of the varying ability of the animals 

 to use certain amounts of the diatoms as they grow, and also because 

 the number of larvae in the dishes varies somewhat, it is impossible to 

 state definitely what amount of diatom culture should be given to the 

 feeding larvae each day. 



Only that amount of diatoms should be fed to the larvae each day that 

 they will clean up well by feeding time on the following day. Due to the 

 transparency of the trochophores it is a simple matter to ascertain if they 

 are feeding well, for the ingested diatoms may be seen massed within the 

 gut. 



Be sure, however, that the amount of material is sufficient to last 

 until the time of the next feeding. An average feeding from an average 

 diatom culture at the beginning of the feeding stage would be about % cc - 

 to each finger bowl containing 50 larvae. It is better to feed less than 

 may actually be used in the beginning, and increase this amount until 

 the correct amount is known. 



SUMMARIZED DIRECTIONS 



A number of important factors to be considered are given below, and if 

 these are carefully observed I think successful results would be quite 

 certain with any free-swimming marine larva that is fairly hardy. 



1. The seawater should be carefully filtered to remove all plank tonic 

 organisms, and unless one is quite certain of the non-toxic condition 

 of the salt water pipe installation of the laboratory, the seawater should 

 be carried in from the outside in a clean glass container. 



2. The temperature should be kept as low as possible, preferably at 

 or below that of the outside ocean water. Guard against any sudden 

 change of temperature. 



3. Not more than 50 to 75 larvae should be kept in a finger bowl at 

 the beginning, and this number should be reduced to 25 or 30 after 

 feeding has become well established and growth has commenced. 



4. Do not put more than three-fourths inch of water in each finger 

 bowl, as more increases the ratio of volume to surface and hence allows 

 less oxygenation. 



5. A good diatom culture for feeding is necessary. The diatom should 



