IOO JEAN DAWSON. 



tube and internal branchiopores. Thus both when the animal is 

 attached and when it is not attached, water must enter the exter- 

 nal branchiopores during inspiration. When the animal is not 

 attached the water thus inspired through the external branchio- 

 pore may possibly be mixed in the gill sac with water inspired 

 through the mouth. Indeed the inspiration of water through 

 the mouth may be one means by which the unattached lamprey 

 secures food. It is generally believed among writers (Mayer, 

 1835 ; Gage, 1893 ; Couvreur, 1897) that water may be inspired 

 through the mouth of the lamprey when unattached. It is 

 possible that breeding lampreys behave differently in this respect 

 from those that are not breeding, but none of these authors state 

 the time of the year in which their observations were made. 



In order to ascertain whether water is normally inspired 

 through the mouth, the following experiment was tried. A 

 breeding Lcnnpetra wilderi was placed in a wire basket which 

 was in turn immersed in a dish of water. The meshes of the 

 basket were small enough to keep the animal from getting out, 

 but afforded no surface to which the animal could attach itself 

 when it came to rest. A carmine mixture was placed near the 

 mouth of the animal when it was thus quiet and unattached, but 

 no current of water could be seen passing into the mouth. Many 

 trials were made, but with the same result. This led me to the 

 conclusion that in the adult lamprey, of this species at least, no 

 current of water is taken into the mouth, but this is of course 

 not true of the larval form. 



On November 29, 1904, two living specimens of IclitJiyomyzon 

 concolor (Kirt), were obtained from the Detroit river and placed 

 in a large aquarium. When one of these was placed on its back 

 without unduly exciting it, the animal immediately became quiet 

 and after a short time, while it remained in this position, could be 

 handled as though it were dead. As soon as it assumed its nor- 

 mal position, however, the animal became active again. The 

 phenomenon seemed to be of a hypnotic nature and obviated 

 the necessity of giving chlorotone to quiet the animal. 



While the animal lay on its back a mixture of carmine and 

 water was poured into the upturned oral funnel. Now and 

 again a red current of water could be seen passing into the 



