113 



female also possessed an indication of the fourth billfurrow and as she 

 was in full breedingdress on March 10th (see Observations on moult, 

 „bird older than two years"). 



It really is remarkable to notice how early old birds sometimes 

 have completely swollen testicles or a strongly developed ovary, 

 especially if we realize that they do not seem to' begin with 

 breeding before the middle of May. 



Haetert (1921) says that the- first eggs in England on the coast of 

 Yorkshire are laid about May 20th, Hantzsch (1905) mentions that the 

 birds of Iceland — also those of the southern part — rarely lay before 

 the middle, mostly not before the end of May or even not before June. 

 According to le Roi (1911) the birds of Beerenisland don't lay before 

 June, probably often not before the middle of that month. The birds of 

 Helgoland however sometimes seem to begin laying much earlier: in 

 1909 Dr. Weigold saw the first eggs on May 10th, in 1912 even on 

 April 22nd (one egg). 



Notwithstanding this late breeding, now and then females from 

 January, at the end of the month, have got ovaries, differing 

 hardly or not from those of April-birds and this is the rule with 

 old females from the first days of March. And whereas the old 

 males from November or December have a left testicle of about 

 10 to 12 mm. long and 3 to 4 mm. broad, the left testicle of one of 

 the males from the beginning of March already measures 22 X 8 ! 



In February and March the testicles and ovaries of the birds in 

 their second spring begin to become much larger for the first time : 

 whereas the breadth of the testicles in such males about the middle 

 of January is about 2 mm., it is in March already 4 mm., in the 

 second half of March a breadth of 5 mm. occurs and a two years 

 old male of April 5th possesses a left testicle which measures 

 already 4 X 20 ! 



It follows from this that there is — in some respect — a relation 

 between the time of moulting and the development of the genitals. 

 This is still better shown by the following. An early moulting 

 bird has its genitals strongly developed early in the year, a later 

 moulting bird has them developed later. This is the case as well 

 with two years old birds as with older ones: a two years old male 

 in March, which was behind several others in moulting, possessed 

 a left testicle of only 2.5 instead of one of 4 mm. width. The most 

 striking instances about relation between moult and development 

 of the genitals are however to be found in young birds, hatched 



