174 Conservation Department 



Development of the Eggs and Larval Life. — The eggs are 

 only about one millimeter (1/25 inch) in diameter and undergo 

 total but unequal segmentation, something like those of the frogs 

 and toads and other amphibia. At first, as stated above, they are 

 sticky, and cling very tightly to pieces of sand and gravel, but 

 after a few hours the covering loses its adhesive quality and the 

 eggs are then free and lie loosely among the sand particles. 



The development begins almost immediately after the eggs are 

 laid and fertilized. The temperature retards if low and hastens 

 if warmer. In an experiment with artificially fertilized 

 eggs with the water at 22.5° Cent. (73 Fahr.) the eggs reached the 

 two-cell stage within six hours. In another experiment they were 

 carried till hatching in the laboratory at about 20° Cent. (70 

 Fahr. ) and it required nine days. In colder water the time is con- 

 siderably extended. When hatched the larvae have a considerable 

 amount of food-yolk remaining, and they stay in the nest until this 

 is used up, from two to three weeks. When the food-yolk is ex- 

 hausted they have reached a stage of development when they 

 can take and digest food. As the microscopic life in the nest is 

 scanty, they migrate down the stream to a mud bank in relatively 

 quiet water. .Here the microscopic organisms are more abundant 

 and they are not so crowded. They secure their food in this way : 

 For breathing the gill chamber is alternately filled with water and 

 emptied. Going in with the stream of water are the microscopic 

 forms on which they feed. In some way, no one knows just how, 

 the young lamprey is able to separate at least a part of the food 

 bodies from the water and pass them on to the intestine where they 

 are digested. Apparently the selection is not discriminative, for 

 particles of sand or any other substanee in the water are passed 

 down to the intestine as well as the infusoria, diatoms, desmids, etc. 

 That only a part of the particles go on to the intestine may be 

 shown by putting one of the ammocoetes in a test tube or slender 

 bottle with water to which a small amount of starch or flour has 

 been added. By using a lens and holding the animal in a good 

 light, it will be seen that a stream flows into the mouth and out of 

 the gill openings or branchiopores. The starch particles help one 

 to follow the stream, and it will be seen that starch grains come out 

 with the expired water. Probably this also happens with the 

 microscopic organisms used for food, that is, only a part of them 

 are made use of. If there is considerable starch in the water one 

 can see very clearly the use of the oral sieve over the opening to the 

 throat (Fig. 1, No. 3). A part of the starch grains is caught b\ 

 the processes making the sieve, and after a while they tend to clog 

 the openings and thus hinder the free entrances of the respiratory 

 water. Any other particles like the silt in muddy water would 



