CYCLIC CHANGES 



IV 



a. 

 b. 



a. 



b. 



c. 



Rest-phase; length, 5 — 8 A.U. 

 Ovulation phase; subdivided into: 



Infiltration phase. The ovipositor lengthens through 

 infiltration with lymph and expansion of the tissue- 

 collagen to a length of about 16 A.U. 

 Inclination phase. During this phase ovulation takes 

 place. The ovipositor may lengthen still further, but 

 only by 3 A.U. at most, reaching a final length of 

 between 16 and 24 A.U. A characteristic of this 

 phase is the oblique position to the female: head 

 down, tail up; hence the term "inclination-phase". 

 Reduction phase. The ovipositor is reduced to the 

 same length as during the rest phase. 



^td stage. Reduction phase. After 

 spawning time the ovipositor tissue 

 atrophies. 



The scheme mentioned above is 

 further clarified by Fig. 80. Outside 

 spawning time the uro-genital papilla 

 is visible, in the form of a small ele- 

 vation between the anus and the anal 

 fin. At this stage, growth of the ovi- 

 positor proceeds extremely slowly. 

 The laying period coincides with the 

 possibilities of oviposition. The in- 

 filtration phase often lasts i 2 hours, 

 but may extend to 24 hours.. 



Within 24 hours, therefore, the 

 greatest lengthening of the ovi- 

 positor takes place. As a rule the 

 inclination phase continues for 24 



24 28 32 



hours 



Fig. 80. Curves of carefully measured ovi- 

 positor growth during the ovulation period 

 in several female bitterlings. 



