354 ON THE MALE OF SPIRULA AUSTRALIS. [Apr. 20, 



at all needed with the female) were traces of acetabula visible (fig. 5, a) : 

 these were merely sessile cupules, not manifesting the peduncular 

 attachment and special structure exhibited in the ' Annals,' pi. i. 

 fig. 6, d, e. The longest, or least-curtailed, of the arms showed 

 a small prominence (fig. 5, a, a) on each side of the base of the hemi- 

 spheric termination (6). 



The testis (fig. 4, o) is a large oblong body, flattened on the 

 ventral (peripheral) side, and extending irregularly centrad into the 

 interspaces of the shell-whorls (fig. 6, o). A. long, slender, convolute 

 sperm-duct (vas deferens, fig. 4, p) conducts the spermatozoa to a 

 wider folded caual with glandular walls {ib. q), which communicates 

 with a csecal prostate, opening into an elongate spermatophorous 

 pouch (?•)• From this a short duct leads to a fleshy hollow penis 

 {ih. s) about 6 niillims. in length. 



The arms which are sexually modified for copulatory actions are 

 the same (viz. the fourth or ventral pair) which are the seat of such 

 adaptation in Sepia &nilLoligo^. But, instead of being " hectoco- 

 tylized," the " brachia copulatores " have lost all trace of acetabular 

 organization in Spirula. The other ordinary arms (i, 2, 3) more- 

 over have that characteristic part of their structure reduced to the 

 rudimental condition in the copulatory arms of Sepia inermis^, and 

 .in a portion of one of those of the male Sepia officinalis^. 



The structures of the digestive, circulating, respiratory (Plate 

 XXXII. fig. 4, br), excretory (hepatic, renal, and melanine), nervous, 

 and muscular systems are identical, or in close accordance with those 

 shown by the female subject of the anatomy of Spirula detailed in 

 the * Annals ' {loc. cit.). In fig. 6 of the present communica- 

 tion a view is given of the outward relations of the shell to its mus- 

 cular and fascial attachments. The disposition of the enveloping 

 portions or origins of the mass of " retractores capitis infundibu- 

 lique" from the terminal chambers is shown at u, fig. 6; the thiu 

 but firm, glistening, fascial investment (f) of the shell is represented 

 as partially reflected therefrom. 



EXPLANATION OF PLATE XXXIL 



Spirula aus&alis c?. 

 Fig. 1. Dorsal view, 



2. Ventral view. 



3. Terminal surface of the body. 



4. Visceral chamber laid open along the ventral side, showing the gills 



and male organs in siHi, with the funnel. 



5. An inner view of the three pairs, 1. 2, ?, of arms and of the mouth, m. 

 5'. The same surface of the terminal portion of the arm, 1, showing the 



acetabul; r modiScation, magnified. 



6. A dissection showing the shell, with its muscular and fascial invest- 



ments, and the " brachia copulatoria," 4, 4'. 

 6 a. Transverse section of the larger " brachium copulatorium." 

 (All the figures, save 5', are of the natural size ; the letters of reference are 

 explained in the text.) 



''■ Steenstrup (Prof. Joh. Japetus Sm.) " Hectocotyldannelsen hos Octopod- 

 slaegterne Arqonauta og Tremoctopxis," &c., ' Kongelige Danske Videnskabernes 

 Selskabs Skrifter, 5te Esekke, 4de Bind,' 4to, 1856, p. 28, tab. i. figs. 1-9. 



2 Loc. cit. tab. i. fig. 8. ' lb. ib. fig. 7. 



