676 SUMMARY OF CURRENT RESEARCHES RELATING TO 



now taken as generic — the number of rostellar hooks — varies in closely- 

 allied species. Inconvenient as these genera are, however, their adoption 

 becomes almost a necessity from the fact that the specific names are 

 often reduplicated in the new genera. For instance, TJrogonimus insignia 

 and Distomum insigne, Prymnoprion anceps and Distomum anceps, &c, 

 though all distinct, yet all strictly belong to the genus Distomum. The 

 author inclines to the device of subgenera as a way out of the difficulty. 

 He further protests against the practice of reviving old names, never 

 adequately defined, in place of well-defined names in common use. 



Nematodes of Coffee-plant.* — Herr A. Zimmermann described in 

 1898 the disease in the Java coffee-plants induced by Tylenchus coffese. 

 He now discusses T. acutocaudatus, which does similar damage. It 

 seems that neither Heterodera radicicola nor Aphelenchus coffese Zn. is 

 injurious to Java coffee-plants. An important fact is that Coffea liberica 

 is relatively resistant to the two species of Tylenchus which attack the 

 Java plant. 



Platyhelminthes. 



Heteromorphosis of Planarians.f — Eina Monti has an interesting 

 note on the occurrence of Planarians, especially Planaria alpina, with 

 two heads or two tails in natural conditions. His object is to show that 

 the heteromorphosis which can be induced experimentally may also be 

 induced mechanically in the streams which the planarians frequent. 



North American Heterocotylea.f — H. S. Pratt gives a very useful 

 synopsis of the North American monogenetic Trematodes, or Hetero- 

 cotylea on Monticelli's system. A diagnostic key to the families, sub- 

 families, genera, and species is given. 



A Distomum with a Genital Papilla. § — Herr L. A. Jagerekiold 

 describes Levinsenia (Distomum) pygmsea Levinsen from the herring 

 gull and the eider duck. It has an enlarged partly muscular genital 

 sinus, which seems to lack the radial musculature distinguishing the 

 true genital papilla seen in species of Coenogonimus and Tocoirema. The 

 author shows how L. pygmsea differs from L. brachysoma ; in fact it may 

 be necessary to place them in separate genera. 



New Trematodes. || — Dr. J. Stafford describes a considerable number 

 of new Canadian flukes, and also gives details as to host, anatomy, &c. 

 of some previously described forms. Of the new species the most 

 interesting is Distomum pelagicum sp. n., which was found in tow-net 

 material from Passamaquoddy Bay, New Brunswick. It is remarkable 

 in having the posterior end of the body invaginated to form a large 

 cavity which opens to the exterior by a narrow opening, and receives 

 (probably) the openings of the excretory canals. The author believes 

 that this cavity is to be regarded as equivalent to a greatly enlarged 

 expulsion canal, and that its function is probably to enable the fluke to 

 swim by the forcible expulsion of water from its interior. Positive 

 evidence of this is however lacking. 



* Mededeelingen uit s'Lands Plontentuin. xxxvii. (1900). See Bot. Centralbl., 

 lxxxiii. (1900) pp. 87-8. t Rend. 1st. Lonibardo, xxxii. (1899) pp. 1314-21. 

 % Amer. Nat., xxxiv. (1900) pp. 645-62 (50 figs.). 

 § Centralbl. Bakt, u. Par., xxvii. (1900) pp. 732-40 (3 figs.). 

 || Zool. Jahrb. (Abt. Svst.), xiii. (1900) pp. 399-414. 



