Rearing of Pelagic Larvm. By J. F. Geinrnill. 249 



Large beakers of flint glass are somewhat easily broken, and 

 accordingly, in fitting up my present permanent arrangement, 

 I employed the knobless bell jars known as wreath-covers. The 

 glass is comparatively thin, and the rounded bottom facilitates 

 equal dispersion of the downward central current, no stagnant 

 corners being left. These bell jars were about lU in. high, held 

 a little more than half a gallon of sea- water, and were set on soles 

 of compressed cork. As they have rather thicker walls than the 

 flint glass beakers, the convection currents are not quite so strong, 

 but they sufficed for the health of my cultures. 



The particular advantage of the arrangement described above 

 is that delicate floating larva3 are protected from possible mechani- 

 cal injury such as is entailed by the use of a stream of air-bubbles 

 or sometimes even of a Brown's plunger. At the same time the 

 method lends itself well to isolation of the aquaria from infections, 

 even those carried by the air. The method can be used for larger 

 or smaller vessels, and a great many of these can be linked on in 

 the same series. 



The amount of tap water employed is not great. I estimated 

 it at 90-100 gallons per day, at the time when the previously given 

 data regarding currents and temperatures were recorded. 



The apparatus has already proved useful along various lines, 

 but perhaps the best testimony to its efficiency is that it enabled 

 me last summer at Glasgow University to rear AsterHas ruhens 

 from an artificial fertilization right through metamorphosis in one 

 or two single aquaria of the size described above, without changing 

 the water in each more than three times during the whole six or 

 seven weeks that elapsed from the time when the larvie were put 

 in as swarming blastulae, until metamorphosis was complete. Of 

 course, great pains were taken in other directions, in order to 

 secure healthy cultures to begin with, and to feed the larvae 

 properly, but the account of these will better be included in a 

 paper I hope to publish on the development of the species in 

 question. 



The convection -current method cannot be expected to take 

 the place of air-bubble aeration for aquaria containing larger 

 sessile animals, or the larger and hardier free-swimming animals 

 or larvae. But wherever small animals are being kept with a view 

 to their spawning if their eggs and larvae are minute and pelagic, 

 or wherever broods of small floating larvie have to be reared, or 

 delicate plankton objects to be kept alive, I think that the method 

 in question, suitably applied to meet particular needs, is likely to 

 prove of use. 



