568 L. K. CRAWSHAY, 



was very high, none living for more than about 15 days, and the 

 average for 8 experiments probably not exceeding 2 days. The few, on 

 the other hand, obtained in the course of the experiment with 

 Acartia, lived for a considerable time. In a few experiments in 

 Position A with mixed plankton kept in its natural proportions, in the 

 water that contained it, from 1 to 3 nauplii were observed alive in 3 

 different experiments in 1-litre flasks, after 11, 11, and 17 days severally ; 

 their continuance in these cases being possibly due to the absence of the 

 initial change of water that was made in the ordinary experiments. On 

 more than one occasion, when nauplii were transferred from townettings 

 to water of a different (higher) temperature, they were seen to be tem- 

 porarily stunned by the change, and to fall to the bottom of the vessel, 

 though usually recovering within some 5 or 10 minutes afterwards. 



Young Calanoids generally, included with some mixed plankton in an 

 11-litre bell-jar of Berkefeld water in Position B, showed a comparatively 

 high maximum in this larger volume of water, several, including nauplii, 

 surviving on the 33rd and a few on the 42nd day. 



There remain for consideration the experiments in Position C with 

 the species Pseudocalanus elongatus, for which unfortunately there are 

 no comparative data in the other positions. Of the 6 experiments which 

 have been referred to, 2 may be omitted in which a sudden failure was 

 attributable to the use of an air-supply. In 3 of the remaining 4 ex- 

 periments, about 50% of the total number of specimens were alive on 

 the 50th day, some being afterwards recorded considerably later ; in the 

 4th probably 30% were alive on the 50th day. Young, which were 

 obtained in all the experiments, were recorded in these four over periods 

 ranging from 40 to 63 days in duration, one or more in each case reaching 



the adult stage. 



General Bemarks. 



While it is not improbable that other adverse causes, in addition to 

 that of changeable temperature, contributed in some measure to the 

 generally unsuccessful results of experiments in Positions A and B, it 

 is difficult to trace them with any consistency, or to attribute the failure 

 of the animals to any single chief cause other than the fluctuations of 

 temperature occurring in vessels which were directly exposed to air 

 changes. 



Experiments with some of the common putrefactive Bacteria, culti- 

 vated on peptone, in no way bore out a supposition that the presence 

 of such Bacteria, and their fouling effects on the water, had exercised any 

 important influence on the progress of the experiments. The possibility 



