1886.] On the Intra-ovarian Egg of some Osseous Fishes. 447 



Average number of micro-organisms 

 found in 10 litres of air by 

 1886. Hesse's method. 



January 4 



March 26 



May 31 



June 54 



July 63 



August 105 



September 43 



October 35 



Experiments are also recorded showing the enormous increase in 

 the number of micro-organisms present in the air of rooms consequent 

 on crowding. In illustration of this point the authors cite a series 

 of experiments made in the Library of the Koyal Society during the 

 evening of the conversazione in June last, on which occasion the 

 following results were obtained : — 



Eoyal Society's Number of micro-organisms 



Library. found in 10 litres of air. 



June 9, 1886. 



9.20 p.m 326 



10.5 „ 432 



June 10, 1886. 

 10.15 a.m 130 



In addition to determining the number of organisms present in a 

 given volume of air, the authors have also, in each case, roughly esti- 

 mated the number falling on a given horizontal surface by exposing 

 dishes filled with nutrient gelatine and of known superficial area, as 

 in the experiments previously published. 



IV. " On the Intra-ovarian Egg of some Osseous Fishes." By 

 Robert Scharff, Ph.D., B.Sc. Communicated by Professor 

 McIntosh, F.R.S. Received November 17, 1886. 



(Abstract.) 



These researches were carried out while acting as assistant to 

 Professor Mcintosh, at the St. Andrew's Marine Laboratory. The chief 

 material consisted of the intra-ovarian ovum of the gurnard (Trigla 

 gurnardus). Many other marine forms, however, were examined. 

 . The paper has been divided iuto the following five paragraphs : — - 



