ARGONAUTIDiE. 23 



is peculiar to the female : its special function is for the protection 

 and i]ieuhation of the eg-g-s. It is not homologous with the 

 chambered or internal rudimental shells of other cephalopods, 

 but may be compared with the cocoon of the leech, or the float 

 of lantiiina. The Argonaut sits in its boat with its siphon turned 

 towards the keel, and its sail-shaped (dorsal) arms closely 

 applied to the sides of the shell It swims by ejecting water 

 from its funnel, and crawls in a reversed position, carrying its 

 shell over its back like a snail. 



The male Argonauts (xvi, 84, 85), are one inch in length, and 

 possess no shell; their dorsal arms are pointed, not expanded. 

 The testis is large, and like that of the Octopus in structure and 

 situation ; it contains spermatozoa of dift'erent degrees of devel- 

 opment, and the excretory- duct probabh' debouches into the 

 hectocotylus. 



A living Argonaut was captured at Long Branch, j^ew Jersey, 

 b}" a fisherman, in August, 1816. It was kept alive for eight or 

 nine days and made feeble attempts to swim in its narrow con- 

 finement (Am. Nat.^ xi, 243). Numbers of fresh shells have been 

 recentlj" dredged, about 90 miles south of Narraganset Bay, 

 R. I., b}^ the TJ. S. Fish Commission. 



The occurrence of the Argonaut on the Florida coast, in one 

 instance with the animal entire, is mentioned in Am. Nat. ,'xii, 39Y. 



Dr. H. Miiller observes that the female Argonaut appears 

 periodically in great numbers at Messina during the spawning- 

 season, but at other times her usual habitat is at the bottom in 

 deep waters. The male is always very small, and is rarely met 

 with : its hectocotylized arm is detached during coition and is 

 found in tht? mantle of the female, where it enjoys a prolonged 

 separate life, although unprovided with digestive organs. The 

 young female an inch in length, has no shell ; it is developed 

 later. 



In South Australia, at certain seasons of the ye&v, during the 

 prevalence of strong northerl}^ winds, the shells of the female 

 Argonaut are washed ashore in considerable numbers. Many of 

 these shells contain the animal in a living state ; but they soon 

 fall a prey to the sea-gulls, by whom they are greedily devoured. 



Suborder II. X>^(7.4POD^. 



Body oblong, laterally finned; arms consisting of eight normal 

 (sessile) ones, and two longer or tentacular arms, which are 

 contractile or retractile ; suckers provided with corneous rings, 

 sometimes armed with teeth, or with hooks ; shell dorsal, internal. 

 One or two of the sessile arms are modified for copulation. 



