specimens utilized were, deliberately selected for length so that 

 all size-groups in the inigrant population would be adequately 

 represented among the data. To obtain a better measure of the 

 variability in egg production at a given size, additional speci- 

 mens were collected in the 17.0- to 18.0-inch (U32-U57 ™^. ) size 

 group. This group embraces the mean length (17.U inches, I1J42 ram.) 

 of the 603 females -viiiich entered Carp Creek in 19U7. 



The earliest specimens represented in ray series of 70 migrant 

 females (iTos. 1, 2, and 3) irere speared just before midnight on 

 April 15 and I6 in Hammond Bay, about 100 feet offshore from the 

 mouth of Carp Creek, They undoubtedly represent the earliest 

 migrants arriving from deeper waters of Lake Huron as determined 

 by repeated observations during the period April 9 through April 1$. 

 Those observed viere malcing no effort to enter the creek at that 

 time. They arrived on the gravel fan off the mouth of the creek 

 about two hours after dark and dropped back into deeper water T,dth 

 the beginning of dawn. Upstream migration began on or about April 

 19. After April 1^-16, specimens for this study were collected at 

 five- to ten-day intervals throughout the migratory period. 



In addition to the gravid females, I4.O spent and dead or dying 

 specimens ^vere collected in the Ocqueoc River, the Little Ocqueoc 

 River (a tributary of the former) and in the Manistique River (a 

 tributary of Lake Michigan). Schoolcraft County (one specimen). 

 The remnants of the ovaries and all eggs remaining in the body 

 cavity were removed and prese2rved in F-A-A. 



(b) Egg development and maturity in sparming migrants 



Female sea lampreys when sexually mature and ripe have a 

 single, elongate ovary extending nearly the entire length of the 

 body cavity (Figure 23). The anterior tip of the ovary begins 

 just behind the last pair of gill pouches and the organ extends 

 posteriorly to the anus. The ovarj^, when the eggs are ripe, or 

 nearly so, constitutes a large percentage of the total weight of 

 the female. In 18 ripe or nearly ripe females collected between 

 June 12 arid June 26, the ovaries averaged 22.14. percent of the total 

 weights of the females and ranged from 13. 6 to 29.^ percent. On 

 the other hand^ in el^t less mature females collected between 

 April 1^ and April 30, at the beginning of the run, the ovaries 

 averaged only 11. 3 percent of the total vreights of the females and 

 ranged from 8„2 tc 15.8 percent. 



■yjlien the eggs are fully ripe, they are shed into the coelom 

 (body oavi.ty) and are forced to the e:jrberior during the spaivning act 

 through a pair of genital pores. One of these pcres enters each 

 side of the urogenital sinus "vdiich is provided T,vith a median pore 

 to the outside on a papilla situated behind anus. No fflllorian 

 ducts (nor vasa efferentia in the male) are present, unless the 



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