<§, 293. THE CRUSTACEA. 350 



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 fronfi^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 oiF, 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 Ci/amus, whose caudal extremity is Taf. IV. fig. 16, 17, f. h. 25) with Idothea ento- 



atrophied, the orifices of the two excretory ducts mon ; but this last author is quite mistaken about 



are situated directly in front of the arms on two, the internal genital organs, having confounded 



side by side papilliform penises {Roussel de the male with the female (loc. cit. p. 12.3, fig. 22). 



Vauzeme, loc. cit. p. 252, PI. VIII. fig. 7, 15). I have already corrected this error in MiiUer's 



With Aei^a, the two testicular tubes are curved S- Arch. 1837, p. 434. Savi!;ny, also (Descript. de 



like on the sides of the CESophagus. Their defer- I'Egypte, Crust. PI. XII. XIII.), has given beauti- 



ent canals are dilated at the posterior extremity ful figures of the copulatory organs of Sphaeroma, 



each Into a seminal vesicle of the same S-hke form. Lyssia, Idothea, Tylos, and Onisciis. The 



They open through two approximated papillae secondary or auxiliary penises have been repre- 



situated on the under surface of the last foot-bear- sented by LerebouZ/et, loc. cit. p. 120, PI. V. fig. 



ing abdominal segment {Rathki, Nov. Act. Nat. 19 {Ly^idium), and by Milne Edwards, Arch, du 



Cur. XX. p. 32, Tab. VI. fig. 16). Mus. II. p. 21, PI. II. fig. 3.* b.i. (Serolis), and 



The three testicles which are found on each side Ann. d. Sc. Nat. XV. 1841, PI. A'l. fig. 4 (Ly^ia). 

 of the thorax with Idothea, Lyssia, Lygidiinn, 15 As to both form and position, the multilobular 



Asellus, Porcellio, Oniscus, &c., are very atten- testicles of SquiUa almost exactly resemble the 



uated in front, but behind, are enlarged into a kind ovaries. But their lateral lobes are not blended 



of bulb before passing into the Vas deferens, together at the anterior extremity of the body, and 



Cavolini (loc. cit. p. 155) has already carefully de- the two deferent canals are given off laterally 



scribed these with Lygia oceanica. See, more- (Delle Chiaje, Descriz. &c. Tav. LXXXVI. fig. 



over, Milne Edwards, Hist. d. Crust. PI. XII. fig. 4). The two penises of these Crustacea have been 



13 (Lygia) ; Brandt, Mediz. Zool. II. p. 76, Taf. correctly figured iu DesmareVs Consid^rat. &c. 



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

 p. 132, PI. V. fig. 134 (Lygidium). For the male organs of My sis, of which the tes- 



1-4 The copulatory organs of the Asellina have tides are composed of only a few lobes, see Frey, 



been described and figured by Brandt (loc. cit. p. loc. cit. p. 26. 



73 and Taf. XV. fig. N.V. Z.). Treviranus, aXiO Vi Cavolini, loc. cit. p. 144, and Milne EOl- 



(Verm.. Schrift. I. p. 59, 74, Taf. VIII. fig. 48, 49, wards. Hist. d. Crust. I. p. 166, and Cyclop, loc. 



Taf. XII. fig. 65-6"), has well represented them cit. p. 783, fig. 418 (Cancer pagurus). 

 with Porcellio, and Asellus, although he entirely 1' Swammerdamm, loc. cit. p. 86, Taf. XI. fig. 6, 



overlooked the six testicles of these Crustacea, and Delle Chiaje, Descriz. &c. Tav. LXXXVI. 



The penis, and its auxiliary stalks, which, with the fig. 6. 



Isopoda are always concealed in the midst of the is Milne Edwards, Ilist. d. Crust. PI. XII. fig. 



branchial lamellae, have been figured by Degeer 15 (Homarus), and Delle Chiaje, loc. cit. Tav. 



(Abhandl. zur Geschichte d. Insekt. VII. p. 191, Taf. LXXXVn. fig. 6 (Scyllarus). 

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



