196 NATURAL SCIENCE. March, 



repeatedly denied, of a ductus vitelio-intestinalis uniting uterus and 

 intestine in Polysionmm (fig. 2), and in its homology with the 

 Laurer-Stieda canal of Digenea. The life-history of the Digenea 

 is exemplified by that of Distomwn macrostonmm (fig. 3) and its 

 sporocyst Leucochloridiuni pamdoxiivi, which, by the way, has been 

 found in two localities in Oxfordshire. The selection is unfor- 

 tunate, for the sporocyst is one of the two most peculiar known, 

 utterly unlike the ordinary form ; and the cercaria is not typical. 

 The anatomy and ordinary form of the sporocyst and cercaria 

 are not described, and the redia is only cursorily mentioned. 

 Yet sporocyst and redia are dimorphic forms of fluke, with a by no 

 means simple structure. A useful table of life-histories is given, 

 and a similar one for certain Cestoda, as well as a second table for 

 the identification of the tape-worms inhabiting man and the domestic 

 animals. Mr. Gamble evidently leans to the view that there is no 

 alternation of generations in the life-history of the majority of tape- 

 worms. Scolex and proglottides are parts of one individual. To the 

 facts adduced it might be added that in Ligula and Schistocephalns it 

 has been said that the vitellaria, their ductules, and the array of testes 

 are continuous throughout the body ; so too with the germaria of 

 Ligiila. In TcBiiia echinococcus the vesicular embryo multiplies qitd 

 vesicle, a number of scolices arising from the secondary, etc., vesicles ; 

 though T. canunis rarely multiplies as a vesicle but always develops 

 many scolices, the two species are regarded as "instances of an 

 alternation of asexual generations in the larval state with a sexual 

 adult state." 



The Mesozoa of E. van Beneden are treated as an appendix to 

 Platyhelminthes, as they are by other authorities. It may be conceded 

 there is no proof of the Dicyemidae and Orthonectidae being forms of 

 life intermediate between Protozoa and Metazoa : there is equally no 

 proof that they are related to one another or that they are derived 

 from platyhelminthic ancestors, simplified by an extreme degeneration 

 due to parasitism. Before a sporocyst was transformed into a 

 dicyemid, its structure must have been sublimed out of recognition. 



In her account of Nemertinea, Miss Sheldon has been able to 

 use the results of Biirger's recent monograph only in the modified 

 classification and the account of the excretory organs with their 

 terminal and platyhelminthic flame-cells. Nothing is said as to the 

 nature of the blood-vessels, whether ccelomic or not. The land and 

 fresh-water forms are enumerated, and in part described, together 

 with the parasitic (?) leech-like Malacohdella. Detailed reference is 

 made to the views of those who find features of alliance to the 

 Chordata. 



The old name Nemathelminthes unites the Nematoda (thread- 

 worms), Nematomorpha {Gordius, Nectonema), and Acanthocephala. 

 It is an echo of Platyhelminthes, and its use, therefore, is to be depre- 

 cated. Mr. Shipley does not base the collocation on phylogenetic 

 grounds, but on convenience and a greater similarity between the 

 three groups inter se as contrasted with other groups of animals. 

 Camerano's argument as to the similarity of the " chief details in the 

 fertilisation aud development of the egg " of Gordius, with the similar 

 processes in Nematoda, does not outweigh considerations of anatomy; 

 and if Kaiser's description of the nephridial organs of GigantorJiyiichus 

 gigas be correct, the Acanthocephala must certainly be severed from 

 the two other groups. An unfortunate error has crept into the 

 account of Rhahdoncma nigrovcnosttm. The parasitic generation in the 

 frog's lung is a female in structure, but, physiologically, a protandric 



