240 J. T. CUNNINGHAM. 



been firmly established as important landmarks in zoology, in 

 the year I have mentioned appeared a memoir bearing the 

 name of L. C. Cosmovici, 1 in which the whole question of 

 segmental organs was thrown into confusion. Overlooking or 

 rather wilfully disregarding the more recent investigations 

 which had brought to light the true relations of the segmental 

 organs, and which had resulted in a generally applicable 

 definition of the organs, this memoir takes the original work 

 of Williams as a foundation, and carefully compares every case 

 examined with Williams' original description. Because 

 Williams did not perceive the glandular nature of the organs, 

 but only their connection with the reproductive functions, 

 Cosmovici defined a segmental organ as a generative duct, 

 while a glandular tube or pouch must be considered and called 

 an organ of Bojauus. As the real segmental organs, or as they 

 are now called nephridia, are usually both glands and genital 

 ducts, they were stated in this extraordinary paper to be usually 

 compound, consisting of a glandular tube, the organ of 

 Bojauus, and a ciliated non-glandular funnel, the segmental 

 organ ; while certain cases were described in which the primi- 

 tive distinctness of the two structures was, as the author 

 believed, retained. Perhaps the most surprising point in this 

 phenomenal paper is that the absence of an internal or coelomic 

 opening is taken as characteristic of the "organ of Bojanus" 

 in the Polychseta, and this in 1880 when to every commencing 

 student of zoology was demonstrated the internal or coelomic 

 opening in the molluscan organ to which the name organ of 

 Bojauus was originally given. It would be best if it were 

 possible to exclude the paper of Cosmovici entirely from the 



Balfour in 1879 (this Journal). The Hertwigs have argued ('Die Coelom- 

 theorie,' 1881), that the excretory organs of Mollusca are not perfectly homo- 

 logous with those of Chgetopoda, Vertebrata, &c, but it has been shown that 

 the pericardial space in Molluscs belongs to a system of mesodermic cavities, 

 distinct from the vascular cavities, and it is pretty generally agreed now, that 

 these mesodermic cavities in Molluscs as well as those in Phatyhelmia re- 

 present a ccelom. 



1 " Glandes Genitales et Organes segmentates des Anuelides Polychetes," 

 •Arch. Zool. Exp.,' Tom. viii. 



