OCR Text |
Show 354 ON THE MALE OF SPIRULA AUSTRALIS. [Apr. 20, at all needed with the female) were traces of acetabula visible (fig. these were merely sessile cupules, not manifesting the peduncular attachment and special structure exhibited in the ' Annals,' pl. i. fi°\ 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 hemispheric termination (b). 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 canal with glandular walls (ib. q), which communicates with a caecal prostate, opening into an elongate spermatophorous pouch (r). From this a short duct leads to a fleshy hollow penis (ib. s) about 6 millims. 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 and Loligo1. But, instead of being "hectoco-tylized," the " brachia copulatores " have lost all trace of acetabular organization in Spirula. The other ordinary arms (l, 2, 3) moreover have that characteristic part of their structure reduced to the rudimental condition in the copulatory arms of Sepia inermis2, and in a portion of one of those of the male Sepia officinalis3. The structures of the digestive, circulating, respiratory (Plate XXXII. fig. 4, 6/*), excretory (hepatic, renal, and melaniue), 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 communication a view is given of the outward relations of the shell to its muscular 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 thin but firm, glistening, fascial investment (v) of the shell is represented as partially reflected therefrom. EXPLANATION OF PLATE XXXII. Spirula australis cS. 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 situ, with the funnel. 5. A n inner view of the three pairs, 1, 2, 3, of arms and of the mouth, m. 5'. The same surface of the terminal portion of the arm, 1, showing the acetabular modification, magnified. 6. A dissection showing the shell, with its muscular and fascial investments, and the " brachia copulatoria," 4, 4'. 6 a. Transverse section of the larger " bracbium copulatorium." (All the figures, save 5', are of the natural size; the letters of reference are explained in the text.) 1 Steenstrup (Prof. Job. Japetus Sm.) " Hectocotyldannelsen hos Octopod-sla3gterne Argonauta og Tremoctopus," & c , ' Kongelige Danske Videnskabernes Selskabs Skrifter, 5te Ksekke, 4de Bind,' 4to, 1856, p. 28, tab. i. figs. 1-9. * Loc. cit. tab. i. fig. 8. 3 Ib. ib. fig. 7. |