260 SYNOPTIC COLLECTION. 



traces of the veliger stage (which has been described in 

 the Pelecypods and Gastropods) are entirely lost by the 

 law of acceleration in development. 



The squid (No. 635, Loligo vulgaris Lam.), has a long 

 body covered with a leathery mantle with a fin on either 

 side of the posterior end. At the forward end the mantle 

 is free, so that the water passes into the cavity of the 

 body, and bathes the two gills which are placed one on 

 either side (see preparation, No. 636). After the water 

 has flowed in, the mantle is applied closely to the neck so 

 that the body cavity is a tight bag with only one opening, 

 and that is the ambulatory pipe or hyponome which we 

 found in the Nautilus. The forcible ejection of the water 

 through this pipe sends the animal swiftly backwards. 

 The waste products of the body and the inky fluid for 

 protection are also discharged through this pipe. The 

 head of the squid is provided with two eyes which are 

 more highly organized than any other invertebrate eye, 

 but have only a superficial resemblance to the vertebrate 

 eye. The mouth has a horny beak and a lingual ribbon. 

 It is surrounded by eight short arms and two long ones 

 which have suckers. In the preparation (No. 636) an 

 incision has been made along the middle of the ventral 

 side, and the mantle laid back exposing the internal 

 organs. A slender tube, the esophagus, extends from 

 the mouth to the long, sac-like stomach which has a bag- 

 like coecum near the pyloric or forward end. The intes- 

 tine, another slender tube, is seen running forward from 

 the stomach under the liver, and by the side of the duct 

 of the ink bag. The anus and the outlet of the duct are 

 near the base of the ambulatory pipe and directly in the 

 path of the outgoing current of water which, as we have 

 already said, carries away the products of both intestine 

 and ink bag. The heart is situated near the base of the 

 gills ; back of it and occupying the greater part of the 

 body cavity is the mass of eggs. 



The embryo of Octopus has a shell sac on the forward 



