lt>4 Miscellaneous. 



feathers and covered with a black, hard, thick skin, overlapped in 

 part by the lengthened frontal plumes. Another, a male from Ca- 

 morta island, is similar ; but the frontal plumes being shorter, the 

 naked callosity is more evident. In a third, a female from Nang- 

 cowry island, the naked area extends almost from the forehead to 

 low down the nape. At the anterior edge of the naked skin is a 

 large fold, the true nature of which it is difficult to ascertain in the 

 dry specimen. 



On tlie Structure of the Caudal Appendage of some Ascidian Larva;. 



By M. A. Giard. 



We know, from the brilliant discovery of M. Lacaze-Duthiers, 

 that certain species of the genus Molgula issue from the egg in an 

 amoeboid form, having no external resemblance to the larvae of the 

 other Ascidia. Kupffer soon extended this discovery to several other 

 types of the same genus. Hancock, on the other hand, has shown 

 that this exceptional mode of evolution does not occur generally in 

 all the species of the group Holgulidaa. Thus Molgula complanata 

 and M. ampidloides have a urodelous larva furnished with a well- 

 developed caudal appendage. I have also indicated some analogous 

 cases, and called the attention of zoologists to the interesting fact 

 that the Molguloe with abnormal embryos are free in the adult state, 

 whilst the regularly constructed larvae belong to species which 

 become permanently fixed. 



The investigation of a species of Molgula which is very common 

 on the shores of the Boulonnais enables me now to enunciate this 

 law with more certainty, and furnishes a new example of a very 

 singular peculiarity of structure which I had previously observed in 

 the caudal appendage of the larvae of the genus Cynthia. 



The rich shores of Wimereux and Portel, to the east and west of 

 Boulogne, are literally carpeted, in the first part of the laminarian 

 zone, by a fine Molgula which, instead of living isolated like its con- 

 geners, occurs in gregarious masses of individuals adhering firmly to 

 each other, and often even rendered polyhedral by mutual pressure. 

 From this mode of life this species might be supposed to be the one 

 described by J. Alder under the name of Molgula socialis (Ann. & 

 Mag. Nat. Hist. March 1863, p. 159) ; but the anatomical characters 

 given by the English naturalist are not sufficient to establish their 

 identity. He does not mention the length of the siphons, which is 

 very remarkable ; the size (half an inch) is less than that of the 

 Wimereux specimens, which average two to three centimetres in 

 height ; lastly, the only specimen of the above species examined by 

 Alder was a colony attached to a Pecten maximm dredged at twelve 

 miles from Hastings. Now the Molgula of the Boulonnais is no 

 longer abundant in deep water, where it is replaced by the twisted 

 masses formed by the tubes of the Hermellce. 



The Wimereux Molgula often establishes itself on the lower surface 

 of stones, but more frequently on the upper surface of the Jurassic 

 rocks (Portland sandstones) which constitute the sea-bottom. The 



