GLASGOW SOCIETY OF FIELD NATURALISTS. 



151 



TABLE OF AVERAGES, 



Showing how many days earlier or later than their average date the arrival of each 

 bird is in each year. The letter "e" indicates that the bird arrived earlier, and 

 the letter 'T' that it arrived later. 





Average 



arrival 



over 10 years. 



1864 



1865 



1866 



1867 



1868 



1869 



1870 



1871 



1872 



1873 



1874 



1875 



Swallow, 



Swift 



15/4 



7/5 



9/5 



14/4 



23/4 



1/5 



22/4 



2/4 



24/4 



25/4 



27/4 



1/5 



12/5 



7/4 



6e 







3^ 



i"i 



i'e 



Z 



le 



11 

 51 







3e 

 11 



11 

 2e 







2e 

 21 



le 

 11 

 5 1 

 21 





 



3e 

 2e 







2e 



11 

 51 

 le 

 21 

 21 

 21 

 21 







fe 



21 



3e 

 11 

 51 







2e 

 11 

 3e 

 2e 





 



2e 

 21 



le 

 11 

 11 

 le 

 2e 

 2e 

 11 

 3e 





 



2e 



21 



2e 







11 

 11 

 11 

 11 

 le 

 8e 





 



2e 

 2 1 



11 

 8e 

 5e 







11 

 2e 

 2e 

 11 







5e 

 21 

 9e 



22 e 

 6e 



11 



2e 





 



11 



31 

 11 



21 







51 

 61 

 61 

 5e 

 5e 



61 

 2e 

 5e 

 11 

 21 







21 

 31 





 



21 

 21 

 4e 

 8Z 



11 

 1 e 



House Marten, 

 Sand Marten,.. 

 Cuckoo 



13 e 

 •61 



3f 



Landrail, 



Nightingale, ... 



Chiff Chaff 



Sedge Warbler, 

 Willow AVren,. 

 White Throat, 



Black Cap, 



Fly Catcher,... 

 Wryneck, 



2e 

 2e 

 51 

 51 

 21 

 21 

 31 

 11 

 21 



Mr. John Harvie next read a paper on " The Alternation of 

 Generations." He confined his remarks to his own observations 

 on the Coelenterata, particularly to the common Medusa or Jelly- 

 fish, Aurelia aurita. After describing the Medusa he traced the 

 development of the little active ciliated organisms produced by it, 

 which after a time affix themselves by the proximal end to some 

 object. This plant-like rooted Zoophyte becomes indented at the 

 free end, and four tentacles are developed. These tentacles split 

 up, and at length a large number are produced. The body 

 becomes ringed, and gradually these rings break ofi^ one by one in 

 cup-shaped forms, and rapidly enlarging develop into Medusse 

 similar to the parent organism. This phenomenon had been termed 

 by Steenstrup the alternation of generations, but there were good 

 reasons for rejecting the phrase as not being one which accurately 

 desci-ibed what took place. Most observers were now of the 

 opinion that the Medusa was not entitled to be called an animal, but 

 was simply an organ of one, and they called it a generative bud or 

 gonophore. The whole question turned on the meaning of the 

 word individual. If an individual be defined to be an animal 

 form that has an independent existence, has the power of assimi- 

 lating food and of reproducing itself, then alternation of genera- 

 tions seemed to be quite an admissible term ; but if an individual 

 be defined, as it had been, as the sum of the contents of a single 



