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XII. On the Testis o/"Limulus. By "W. B. S. Benham, Esq. (Communicated by 

 Prof. E. Rat Lanejestek, II A., F.L.S.) 



(Plate XXXVIII.) 



Read June 21st, 1SS3. 



WHILE working in the laboratory at University College, last October, as one of Prof. 

 E. Ray Lankester's assistants, he suggested that I should examine the testis of the King- 

 Crab. By his kindness (here I will take the opportunity of thanking him for his kind 

 help and suggestions) I was fortunately able to work on the fresh animal. Owing 

 to the difficulty, and the time taken, in removing the carapace, not much could be 

 done in a day ; and though it kept fresh till the next day, after that it had to be placed 

 in spirit ; in this state the finer networks are easily broken, and the finer blood-vessels 

 may be mistaken for the ducts, though the mistake is soon discovered, owing to the 

 absence of networks in the former. The testis is packed by the ramifications of the 

 gastric gland (the so-called liver), and lies almost superficially. 



The only description of the generative organs of the King-Crab appears to be that by 

 Prof. Owen, which was published in the Linnean Transactions for 1873. He there 

 describes and figures a portion of an ovary ; his description opens thus : — " The ovarium 

 is a system of ramified tubes and cavities, occupying chiefly the dorsal region of the body ; 

 it extends along the median part of the thoracetron" ( = abdomen), " and expands laterally 

 in the cephaletron " (cephalothorax). His figure shows rather thick ducts; and the network 

 represented is not extensive, but, so far as it goes, corresponds roughly with the distri- 

 bution of the testis. It may be said that the testis forms a reticulated tube all over the 

 dorsal portion of the thorax and abdomen, mixed up with the liver. Owen divides the 

 ovary into anterior and posterior median lobes, with anterior, lateral, and postero-lateral 

 branches and networks proceeding from the former lobe. 



We can scarcely, as will be seen, divide the network of the testis into such lobes, though 

 roughly there are anterior (thoracic), posterior (abdominal), and lateral (thoracic) net- 

 works. As in the ovary, the main duct of the testis, from the external aperture, divides, on 

 reaching the surface of the liver, into three main branches, having about the same course 

 as in the female organ. 



Professor Owen's figure represents the branches as symmetrical on each side ; such is 

 ' not the case with the network of the testis, as will be seen. He suggests as a cause for 

 the posterior median lobe of the ovary dividing into two branches, at the junction of 

 abdomen and thorax, which run forward to the anterior median lobe, that the pressure 

 on it, between heart and intestine, which would take place on flexion of the abdomen on 

 the thorax would be too great if median, and hence there is a branch on each side, out- 

 side the pericardium. In the case of the testis, the ducts are much smaller than those 



SECOND SERIES. — ZOOLOGY, VOL. II. 53 



