ON MYSIS. 2^ 



contractions of their muscular fibres, as represented in the 

 fi£i;ure, and seem to be lost at length in a great sinus or 

 auricle, lying beneath the heart ; whether this is really the 

 case or not, remains to be ascertained by dissection, there 

 can scarcely be a doubt however, that the tw^o large veins 

 constitute the Vena? porta*, and ultimately send their 

 blood to the Branchia : a somewhat similar appearance, is 

 presented by the venous system of the Caligi, and it is not 

 improbable that in both of these, a valvular communica- 

 tion will actually be found to exist between the posterior 

 commencement of the above described Venae portae and 

 the abdominal cavity, into which cavity, we may suppose 

 the fluids to be finally poured by the continuations of the 

 arteries, and by the excretorics of the alimentary canal, 

 taking into consideration at the same time, that no lacteals 

 or lymphatic system has been proved to exist in any of 

 the invertebrated animals. Whether these appearances, 

 independent of dissection, warrant such a view of the 

 circulation or not, Physiologists will be enabled the better 

 to appreciate its probability, by referring to a somewhat 

 similar contrivance in the molluscous genera of Aplysia 

 and Sepia, first brought to light by the immortal labours 

 of the first comparative anatomist of the age. See Cuvier, 

 Memoires pour servir a I'Hist. Nat. des Mollusques. 



If the Opossum Shrimps are the prey of numerous 

 inhabitants of the ocean, they are themselves equally 

 destructive to animals less in size and power, being how- 

 ever rather omnivorous, than strictly carnivorous, seizing 

 and eating every animal substance which the current or 

 the tide carries along with it, and contending like vultures 

 for the possession of the larger masses, nothing tends 

 however to establish more unequivocally their rapacious 

 nature, than the circumstance, that when confined together 

 in a vessel of sea water, they even kill and devour one 

 another. 



