ON THl^ DEVELOPMENT OF SAGITTA. 355 



remained inside the shell; and therefore its action on the 

 tissues was too much prolonged. 



At Naples eggs ot" several species were obtained, some in 

 May and June, by searching the " Auftrieb " with a lens as at 

 Faro j but since many species are common at Naples, these 

 could not be identified with certainty. 



The most satisfactory method was to put a number of 

 Sagitta in a jar with two or three litres of fresh sea water, and 

 next day by draAving off the lower layer of water with a 

 syphon the eggs could be found. In this way a large 

 number of eggs of S. enflata were obtained in the autumn 

 of 1900 (from November 1st to December 11th), and again in 

 the spring of 1901. In the cold weather no eggs were laid ; 

 the last were obtained on December 11th, and the first in the 

 spring on March 8th. These eggs developed more slowly 

 than those obtained in Sicily, possibly in consequence of the 

 lower temperature, for it was noticed that the development 

 took longer as the weather got cooler. They were also less 

 regular than the Sicilian species. At 9 a.m. all stages from 

 the unsegmented egg up to well-developed gastrulse were 

 found, and hatchiug took place usually but not always on the 

 following day. In Sicily it was not found possible to keep 

 alive the young Sagitta more than a few hours after hatching, 

 but the S. enflata larva) at Naples were kept easily for a 

 week, and in one case for fifteen days. They were kept in 

 jars of about three litres, covered with a glass plate, and 

 without any especial care would live for several days. Those 

 that lived for the longest time were kept at an even tem- 

 perature by placing the jars in running water, and once or 

 twice a day fresh sea water was run in, in such a way as to 

 carry down bubbles of air to aerate the water. The young 

 Sagitta always remained near the surface, so that the water 

 could be drawn off with a syphon from below to make room 

 for the fresh supply. The water was in no case filtered, and 

 the temperature ranged from 16*5° to 18*5°. 



I also obtained eggs from S. bipunctata at Naples during 

 April and ^lay, and kept the young alive for several days. 



