320 CEYLON PEARL OYSTER REPORT. 



Tentacles large and numerous, all one size, bases touching, about 80 in all (fig. 39). 



Dorsal Tubercle simple, with an anterior opening and the horns rolled slightly 

 inwards in one specimen (fig. 44) and turned outwards in another (fig. 43). 



Alimentary Canal with an open loop and a closely ridged stomach ; but it may, like 

 the branchial sac, be completely absent. 



Gonads. A row of about 14 yellow sausage-shaped polycarps on the right side of 

 the body and fewer on the left. Many endocarps on both sides. 



Locality : Station LIV., in north part of Gult of Manaar, 4 to 40 fathoms, three 

 specimens. 



Of the three specimens of this species obtained together at the one spot, two are in 

 an interesting condition. The sjjeciinen shown in fig. 38, and from which the above 

 description has been drawn up, is perfect and normal in all its organs ; but the other 

 two which, externally, seem as well grown and as complete (see fig. 34), were found 

 on dissection to have no alimentary canal and no branchial sac (see fig. 35). 



Sluiter, in 1885, described a single specimen of a Styela which he found at 

 Billiton, in the Malay Archipelago, under the name Styeloides abranchiata, as a new 

 species belonging to a new genus because of the absence of branchial sac and 

 alimentary canal. As it was scarcely possible to believe that such could be the 

 normal condition of the species, in my 'Revised Classification of the Tunicata' 

 (p. 578), in 1891, I expressed some doubt and suggested that Sluiter's specimen was 

 an individual abnormality. 



In 1895, Sluiter, in his "Report on the Tunicata of the Semon Expedition," 

 described a new species, Styela solvens (Semon, ' Forschungsreisen,' Bd. v., p. 182), 

 in which, out of three specimens found at Amboyna, the branchial sac was absent in 

 two and the intestine in all. This observation caused Sluiter to relinquish his 

 genus Styeloides, and suggest that in the species of Styela in question the branchial 

 sac, &c. might become lost as a normal process. The following year, however, 

 Willey, in his "Letters from New Guinea" ('Quart. Journ. Micr. Sci.,' 1896, 

 p. l(il), described the ejection of the viscera which he had actually observed in a 

 species of Styela which he, following Sluiter, named Styeloides eviscerans. Sluiter 

 refers further to the three mutilated species, Styela abranchiata, St. solvens, and 

 St. eviscerans in his paper on Weber's South African Tunicata (' Zoolog. Jahrb.,' 

 1898), and raises the question whether regeneration can be in progress in such cases. 

 Finally, two additional specimens of Styela abranchiata, both also in the mutilated 

 condition, were obtained by the " Siboga " expedition. 



The condition of affairs in the three specimens front Ceylon, which I am now 

 describing as Styela mutilans, confirms the impression I expressed in the ' Revised 

 Classification' in 1891, and upon which agreement seems now to be general. 



The Ceylon specimens do not belong to any of the previously described species of 

 Sluiter or Willey. They differ from all in various particulars, and belong clearly 

 to the genus Polycarpa ; but here is a case where, if the first specimen which 1 



