Table 3 makes such a comparison in 10 females 

 taken a few weeks preceding the spawning season. 

 An end-point fluctuation of plus or minus one serial 

 dilution can be anticipated as part of the experi- 

 mental error inherent in the technique (Kabat and 

 Mayer, 1961). Only one fish e.xceeded this range. 



Table 3. — Cotnparative titers of HM factor in kidney-tissue 

 fluid and serum of 10 English sole 



*Reci|irocal of last positive dilution. 



In 19 female halibut, where kidney fluid and serum 

 samples were obtained from freshly caught individ- 

 uals, identical qualitative results were observed for 

 every fish. In the halibut sample taken during 

 June 1962, kidney fragments were obtained from 

 carcasses that had been eviscerated and iced for 4 

 days, but serum samples were obtained from the 

 same fish when freshly taken. Qualitative tests 

 were made with both serum and kidney fluids. 

 Quantitative tests were made with those sera which 

 gave positive double-diffusion reactions (table 4). 

 The only disagreements between the qualitative 

 data for the kidnej^-tissue fluids and serum were the 

 three individuals with the lowest serum concentra- 

 tion. The 4-day icing of the cleaned halibut carcass 

 doubtlessly diluted the HM concentration in the 



Table 4. — Comparison of HM titer of blood serum in halibut 

 with double-diffusion reaction of kidney-fragment fluids col- 

 lected from, the same individuals 3 to 4 days after evisceration 

 and icing 



*ReciprocaI of last positive dilution. 



adhering kidney fragments; it seems likely all tests 

 would have agreed if the kidney tissue had been 

 fresh. 



The above evidence indicates that serum and 

 freshl}' taken kidney-tissue fluids can be used inter- 

 changeably with considerable confidence for detec- 

 tion of the HM factor in these two species when 

 qualitative data are desired. 



ANALYSIS OF DATA ON ENGLISH SOLE 



The six stages used by Hagerman (1952) to des- 

 cribe development of the ovary in the Dover sole 

 were modified in the following manner to describe 

 the development in the English sole: 



Immature: 



A. Ovaries very small (generally less than 1 g.), 



white, transparent, and somewhat gelati- 

 nous. 

 Mature : 



B. Developing. Ovaries enlarging, becoming 



yellowish and opaque. Developing egg 

 visible macroscopically. 



C. Gravid. Ovaries very full of yellowish 



granular eggs. 



D. Spawning. Ovaries full of transluscent eggs 



which run under slight pressure. 



E. Spent. Ovaries flaccid; ovarian membrane 



vascular and sac-like. 



F. Resting. Ovaries firm, white, transluscent, 



and somewhat gelatinous. Distinguished 

 from stage A by the greater size. 



The scale was not universally applied in this study 

 owing to the overlap among the various stages. 

 Stages A and F, in particular, were often difficult to 

 distinguish; however, in November through Feb- 

 ruary, including the peak of spawning in December 

 and January (Holland, 1954; Harry, 1959), the 

 stage A ovaries were distinct because stage F ovaries 

 were lacking. All individuals taken during this 

 period with ovaries in stages B through E were HM 

 positive. 



Certain individuals with stage A ovaries surpris- 

 ingly were HM positive during the spawning season 

 (table 5). Maturity classifications were made on 

 these gonads, which were fixed in formalin, ^^'hen 

 state of maturity is not listed, the ovaries had been 

 sectioned for histological examination before any 

 e.xternal maturity classification was attempted. The 

 two individuals with mature gonads had ovaries in 



SERUM FACTOR IN MATURITY 



51 



