^293. 



THE CRUSTACEA, 



359 



which, with the Idotheoidae, and Asellina, are two pairs of similar seminal 

 tubes. The two Vasa deferentia converge towards the posterior portion of 

 the body, where they pass into a double, or a single excretory canal, which 

 usually commences directly in front of the first pair of post-abdominal feet, 

 on the median line of the body.'^^' With the Isopoda, this excretory canal 

 opens into a short, backwardly-curved penis, upon which are two long • 

 processes (secondary penises) inserted on the internal border of the second 

 pair of feet. ^"' 



With the Stomapoda, the testicles consist of more or less ramified, gland- 

 ular lobes, from which pass ofi", laterally, two Vasa deferentia which ter- 

 minate in two hollow penises projecting at the base of the last pair of 

 feet.^i^> 



With the Brachyura, and the short-tailed Anomura, the two testicles 

 consist of a net-work of very small semeniferous canals, occupying the lat- 

 eral portions of the cephalothorax, which gradually increase in size until 

 they pass into the long Vasa deferentia. These last form numerous convo- 

 lutions, and are finally continuous into two larger Ductus ejaculatorii.'-^^^ 

 With the male Paguridae, the testicles are contained, like the ovaries, in 

 the tail. They consist of two large tubes which rapidly contract into a Vas. 

 deferens, which is straight, at first, but afterwards spiral. This then 

 becomes larger and is gradually continuous into a Ductus ejaculatorius/^^'^ 



With some Macrura, the cephalothorax contains two anterior and two 

 posterior testicular tubes, a portion of the last being extended even into 

 the tail ; while the first are connected, by a transverse anastomosis, behind 

 the middle of the body. The two posterior join with the two anterior in 

 the posterior extremity of the cephalothorax, and form on each side, a short, 

 narrow, deferent canal, which terminates in a larger Ductus ejaculatorius.'-^^^ 



13 With Ct/amus, whose caudal extremity is 

 atrophied, tlie orifices of the two excretory ducts 

 are situated directly in front of the arms on two, 

 side by side papilliform penises {Roussel de 

 f^auzeme, loc. cit. p. 252, PI. VIII. tig. 7, 15). 

 With Aes;a, the two testicular tubes are curved S- 

 like on the sides of the oesophagus. Tlieir defer- 

 ent canals are dilated at the posterior extremity 

 each into a seminal vesicle of the same S-like form. 

 They open through two approximated papillae 

 situated on the under surface of the last foot-bear- 

 ing abdominal segment {Rathki, Nov. Act. Nat. 

 Cur. XX. p. 32, Tab. VI. fig. 16). 



The three testicles which are found on each side 

 of the thorax with Idothe.a, Lygia, Lygidimn, 

 Asellus, Porceilio, Oniscus, &c., are very atten- 

 uated in front, but behind, are enlarged into a kind 

 of bulb before passing into the f-'as de/ercns. 

 Cavolini (loc. cit. p. 155) has already carefully de- 

 scribed these with Lygia oceanica. See, more- 

 over, Milne Edwards, Hist.d. Crust. PI. XII. fig. 

 13 (.Lygia) ; Brandt, Mediz. Zool. II. p. 70, Taf. 

 XV. fig. 31 (Oniscus), and Lereboullet, loc. cit. 

 p. 132, PI. V. fig. 1.34 (Lygidium). 



14 The copulatory organs of the Asellina have 

 been described and figured by Brnndt (loc. cit. p. 

 73 and Taf. XV. fig. N. V. Z.). Treviranus, also 

 O'erm. Schrift. I. p. 59, 74, Taf. VIII. fig. 48, 49, 

 Taf. XII. fig. 65-67), has well represented them 

 with Porceilio, and Asellus, although he entirely 

 overlooked the six testicles of these Crustiicea. 

 The penis, and its auxiliary stalks, which, with the 

 Isopoda are always concealed in the midst of the 

 branchial lamellae, have been figured by Degeer 

 (Abhandl. zur Geschichte d. Iiisekt. VII. p. 191, Taf. 

 XXXII. fig. 6, 20), and by Rathke (loc. cit. p. 125, 



Taf. rv. fig. 16, 17, f. h. 25) with Idothea ento- 

 mon ; but this last author is quite mistaken about 

 the internal genital organs, having confounded 

 the male with the fem.ale (loc. cit. p. 123, fig. 22). 

 I have already corrected this error iu Muller''s 

 Arch. 1837, p. 434. Savigny, also (Descript. de 

 I'Egypte, Crust. PI. XII. XIII.), has given beauti- 

 ful figures of the copulatory organs of Sjihaeronia, 

 Lygia, Idothea, Tylos, and Oniscus. The 

 secondary or auxiliary penises have been repre- 

 sented by Lereboullet, loc. cit. p. 120, PI. V. fig. 

 19 (Lygidium), and by Milne Edwards, Arch, du 

 Mus. II. p. 21, PI. II. fig. 3.* b.i. (Scrolls), and 

 Ann. d. Sc. Nat. XV. 1841, PI. VI. fig. 4 (Lygia). 



13 As to both form and position, the multilobular 

 testicles of Squilla almost exactly resemble the 

 ovaries. But their lateral lobes arc not blended 

 together at the anterior extremity of the body, and 

 the two deferent canals are given off laterally 

 (Delle Chiaje, Descriz. &c. Tav. LXXXVI. fig. 

 4). Tlie two penises of these Crustacea have been 

 correctly figured in DesmareVs Considerat. &c. 

 PI. XI^II. n. n. 



For the male organs of Mysis, of which the tes- 

 ticles are composed of only a few lobes, see Frey, 

 loc. cit. p. 26. 



1<! Cavolini, loc. cit. p. 144, and Milne Ed- 

 wards, Hist. d. Crust. I. p. 166, and Cyclop, loc. 

 cit. p. 783, fig. 418 (Cancer pagurus). 



17 Swammerdamm, loc. cit. p. 86, Taf. XI. fig. 6, 

 and Velle Chiaje, Descriz. &c. Tav. LXXXVI. 

 fig. 6. 



18 Milne Edwards, Hist. d. Crust. PI. XII. fig. 

 15 (Homarus), and Delle Chiaje, loc. cit. Tav. 

 LXXXVII. fig. 6 (Scyllarus). 



