CCELENTERATA AND 



come quiet. It is well also to place the dish in such a 

 way that direct light shines on one side in order to look 

 through it from the other. The black ground and the 

 light passing through the water make it possible to detect 

 more easily sm al swimming larvae. Commonly also, 

 when the water in the dish is quiet, the minute embryos 

 and larvae come to the surface and can be seen and easily 

 picked out with a pipette, from which they are transferred 

 to a "live box," or watch crystal for study. 



The present work goes no farther than the identifica- 

 tion of the larvae. Their method of treatment as objects 

 of embryological research with reagents and with the mi- 

 croscope belongs to another chapter of marine zoology. 

 Those who seek in these pages a fauna! catalogue will 

 find many omissions. I have tried to write an introduc- 

 tion to the fascinating study of the adult and larval stages 

 of the lower animals which are found in our bays. 



(7. COLLECTING SURFACE ANIMALS. 



(WITH TOW OR DIP-NET.) 



The animals which constitute the surface fauna are ob- 

 tained by what is called a towing-net. The towing-net is 

 a bag made of strong linen or bunting and is dragged 



TOW-NET FOR ^SQUORIAL ORGANISMS. 



through the water after the boat. The mouth of the net 

 is kept open by a metallic ring to which the mouth of the 

 net is fastened. The net should be about a foot deep, and 



