Biological Survey — Oswego Watershed 177 



astonishment some of the large larvae showed no change. These 

 were kept over the winter and following summer. They com- 

 menced to transform in August, 1914, but one not until September 

 (Fig. 4, No. 8) . That is, some of the full length larvae lived a whole 

 year after they had reached full size before they commenced to 

 transform. As one can find larvae as long or longer than many 

 transforming ones any month in the year, it is believed that all of 

 them live a year in the larval stage after they reach full length. If 

 this is a correct conclusion, then one year must be added to every 

 estimate based upon size of larvae. From present knowledge it 

 seems to me that the time passed in the larval period in the mud 

 must be at least five years (Figs. 4, 5). 



Transformation of the Larva to the Adult Condition. — 

 When the larval lamprey attains a certain definite maturity, which , 

 as shown above, may take a year after it has reached full length 

 (5 to 7 ] /2 inches), the process of structural changes begins to pre- 

 pare it for its free-swimming, predatory life. The hooded, horse- 

 shoe shaped mouth with an upper and lower lip gradually changes 

 to a circular disc-shaped mouth. The sieve over the throat disap- 

 pears, and on the circular disc appear numerous horny teeth, and 

 in the throat appears a piston-like tongue armed with a double row 

 of rake-like, horny teeth (Figs. 1, 4). 



The eyes instead of being rudimentary and deeply imbedded in 

 the tissues of the head, appear at the surface and have a trans- 

 parent cornea, A good crystalline lens and a more perfect retina, 

 and eye muscles are developed. In place of the single chamber for 

 food and respiratory water in the gill region, a separate oesophagus 

 and bronchus are formed, and the gills are arranged in seven sep- 

 arate sacs or pouches, each with an external opening (external 

 branchiopore) and an opening to the common bronchus (internal 

 branchiopore ) . 



Buccal glands for producing the anticoagulating secretion are 

 developed and their ducts open into the mouth just below the rasp- 

 ing tongue (Fig. 6). The liver loses its gall bladder, and its duct 

 leading to the intestine, so that in its adult life the liver has no 

 duct opening into the intestine. The intestine is also much modi- 

 fied. Many other profound changes occur and finally the young 

 lamprey is ready for its predatory life. At transformation the 

 different lampreys are of about the same size, the brooks being 

 slightly longer than the sea and the lake lamprey. The brook 

 lamprey never increases in size, but as shown in the diagram (Fig. 

 7) the lake and the sea lamprey increase greatly. 



As larvae they all look so much alike that up to the present no 

 clear distinctions have ever been made, but very early in the trans- 

 formation stages, the color changes and the breadth of the oral 

 disc mark differences evident to any one. The brook lamprey 

 changes very little in general coloration, but the sea and the lake 

 lamprey change from the chestnut brown-black of the larva to 

 blue-black. Indeed everywhere they are known by the fishermen 

 as "blue lampers, " and are greatly prized for bait (Figs. 4, 5). 



