REPORT ON THE CIRPJPEDIA. 13 



secrete a thin viscous fluid which envelops the eggs. When no eggs pass through the 

 oviduct the secretion continues incessantly, and in this way a thick mass is formed. 



It is not my opinion that this little sac is a iiseless organ, and 1 believe that, after 

 all, the interpretation of Krohn is more in accordance with the facts than that of Koss- 

 mann. The latter author, moreover, made an elaborate study of Anelasma sqvalicoln,' 

 with the intent to show that this Cirriped is not " in an embryonic condition," as 

 Darwin supposed, but in a rudimentary state in consequence of its parasitic mode of 

 life. The root-like ramifications of the peduncle — observed by Darwin — do not 

 serve only to attach the animal to the skin of the shark (as was supposed by Darwin) ; 

 with their aid the Cirriped sucks the greater part of its food out of the skin of 

 tin' animal in which it is embedded. The simple, degenerated, condition of the parts 

 of the mouth and of the cirri is a rudimentary state in consequence of disuse. No 

 details are given as to the condition of the intestinal tract in the animal in question : 

 whether it is in open communication with the connective tissue of the peduncle, &c. 

 The rootdike excrescences of the peduncle of Anelasma are compared by Kossmann with 

 the roots of the parasitic Cirripedia, and according to this author Anelasma squalicola 

 is an intermediate form uniting together Lepas and the parasitic Cirripedia. 



Embryologieal papers have appeared in great variety since the publication of Darwin's 

 book. It is not my intention to enter into detads upon each of them ; I only wis]) to 

 trace the present condition of our knowledge concerning the Cirripedia. The curious 

 metamorphosis of the Crustaceans of this Order discovered by Thompson, 2 is amply 

 discussed in Darwin's Monograph. The researches made and published during the 

 last thirty years bear almost entirely upon the segmentation of the egg and the 

 formation of the blastoderm, which processes, since the publication of the papers of 

 Filippi, 3 Munter and Buchholtz, 4 Hoek," and Lang, 6 are tolerably well known. On the 

 contrary, we are quite left in the dark as to the way in which the different organs are 

 formed, what we are to understand by germinal layers in the case of the Cirripedia, &c. 



Again, the result of the development within the egg is well-known. The Nauplius- 

 larva, considered by the older observers ' as a full-grown animal, has been recognised 

 since the discovery of Thompson, as the larval form presented by the Cirripedia when 

 first hatched. A second series of papers treats of the metamorphosis this larva undergoes 

 before reaching the adult state, and compares the development of the Cirripedia with 



1 Kossmann, he. cit., p. 180. 



2 Thompson, J. V., Discovery of the metamorphosis in the second type of the (.'impedes, viz., the Lepades, com- 

 pleting the natural history of these singular animals, &c, Phil. Tran.-:, 1S35. 



3 Filippi, F. de, Ueber die Entwicklung von Dichelaspis darwinii, Moleschott, Untersuch., Bd. i.\. 1865. 



4 Munter und Buchholz, Ueber Balanus improvisus, Darw., var. gryphicus, Munter, Abth. 2 Mittheil. a. <l. 

 Katuru'iss. Verein. v. Neu-Vorpomnurn u. Eiigen, i. 1869. 



6 Hoek, P. P. C, Embryologie von Balanus, Niederland. Archivf. Zool., Bd. iii. 187G. 



6 Lang, A., Die Dotterfurchung von Balanus, Jtnaische Zei'scl.r., Bd. xii. 1878. 



7 0. F. Muller and others. 



