Its glowing red eyes narrowed into slits then closed.
Most fish have gill slits on the sides where the head joins the body.
Just below the kneejoint there is a swelling, along which two narrow slits run lengthwise.
The development of these organs, which in the Protonemertine are but grooves in the epidermis, not far removed from the similar cephalic slits of many Turbellaria, reaches its height in Drepanophorus.
These slits are continued into the ciliated duct, being at the same time themselves very strongly ciliated.