10 THE VOYAGE OF H.M.S. CHALLENGER. 



beautifully illustrated. Heller's " Uutersuchungen " commenced in 1874, and the last 

 part published (Abth. iii. 1) appeared in 1877. The work is devoted to a description 

 of the Simple Ascidians of the Adriatic and Mediterranean seas, and commences with an 

 account of the anatomy of Ascidia mentula. In the succeeding systematic part a number 

 of new species are described, most of them briefly, a few with a considerable amount of 

 mical detail. Kupffer's report upon the Tunicata collected by the German North Sea 

 Expedition contains descriptions of several new Simple Ascidians, and anatomical notes 

 upon some imperfectly known species. 



An important paper by Fol, which appeared in 1874, must not be overlooked. It 

 gives an account of the structure and function of the endostyle, showing its glandular and 

 non-nervous nature. 



In 1875 Kowalevsky's elaborate memoir upon the development of Pyrosoma was 

 published. Huxley had long before (1862) investigated this genus, and described the 

 remarkable " Cyathozooid " which gives rise to the first " Ascidiozooids " of the colony. 

 Kowalevsky's researches confirmed Huxley's discovery, and gave fuller details of some of 

 the stages. 



In the same year Todaro's and Brooks' elaborate but in some points rather conflicting 

 accounts of the development of Salpa made their appearance. 



In 1880 a paper appeared upon the Simple Ascidians of the seas of Denmark by 

 Traustedt, containing descriptions of a number of old and imperfectly described, and a few 

 new, species. It also settled some questions of priority in naming, and gave very full lists 

 of the synonyms of the species. A second paper by the same author has just appeared 

 (1S82), containing descriptions of some new West Indian species of Ascidiidse. 



In 1881 a very important memoir by C. Julin was published in the Archives de 

 Biologic This paper gives the results of anatomical investigations into the condition of 

 the nervous system and some neighbouring organs in a few species of the Ascidiidse. 

 Julin corroborates Ussow's account of the relations of the subneural gland to the olfactory 

 or dorsal tubercle, and further declares that the latter organ is nothing more than the 

 complicated aperture of the duct from the gland, and that it has nothing whatever to do 

 with an olfactory or any other sensory function. Julin considers that the gland is homo- 

 logous with the pituitary gland of vertebrates, and that the duct and aperture into the 

 branchial sac represent the embryonic connection of the pituitary gland with the pharynx. 

 In a second paper published in 1882 Julin extends his observations to two other species 

 of Ascidia, and enunciates a theory suggested by Professor E. van Beneden that the 

 subneural gland in the Ascidian, and the pituitary gland in the vertebrate embryo have a 

 renal function, and may be considered as kidneys specially developed for the elimination 

 of effete matters from the blood circulating in the neighbourhood of the central nervous 

 system. 



