ZOOLOGY AXD B0TA5fT, MICEOSCOPT, ETC. 741 



The embryo is said to be developed by the growth of the inner 

 cellular mass, and at the expense of the surrounding secondary yolk- 

 spheres. After the embryo has grown so much that it occupies the 

 whole length of the egg, a papilla appears at its anterior end, and two 

 annular furrows and a pigment-spot become developed. Before the 

 embryo leaves the egg it becomes provided with an investment of 

 cilia. On escape the embryo has the form of an elongated cone, with 

 an average length of "125 mm. and an anterior breadth of '027 mm. 

 The eye-spot is said not to resemble " the sign of multiplication as 

 has been described," but to be really double and made up of two 

 crescentic masses of dark pigment. Midway between the extremities 

 of the body, and on the right and left of the middle lines, are two 

 funnel-shaped spaces provided with cilia in constant motion. 



There is an appearance of probability in the supposition that the 

 already mentioned anterior papilla has a boring function. 



We now come to the important question of the fate of this embryo. 

 We should expect to find it makiug its way by boring into some 

 animal — probably a mollusc — but this has not yet been observed 

 by Mr. Thomas, though he has no doubt as to its occurrence ; nor has 

 he been able to find the sporosac which should result from this 

 boring in any of the Mollusca he has found on infested fields. Where, 

 however, observation fails induction comes to our aid, and the author 

 quotes a commtmication of Professor Eolleston to the ' Zool. Anzeiger ' 

 in which that lamented naturalist accuses the " black slug " or " the 

 smaller of our two British Arions " (J., ater or A. hortensis) as being 

 the intermediate host. 



The author enters into some account of certain laboratory ex- 

 periments and into a history of visits to infested pastures in the 

 neighboui'hood of Oxford ; in one case only one specimen of the black 

 slug was found, though the grey one (A. agrestisj was very common. 

 Thirty specimens of this last were dissected, " but nothing could be 

 found in them." The influence of rabbits is discussed, and the paper 

 concludes with some practical hints on the prevention of rot, which 

 were drawn up by Professor Eolleston and the author. 



Trematoda of Greenland.* — ^M. G. M. E. Levinsen describes the 

 following new species of this group : Distomum MueUeri, D. raollis- 

 simum, D. ocidatum, D. sobrinum, D. somaterice, D. pygmceum, Gyro- 

 dactylus grcenlandicus, and BucejjJiahis crux ; the last species receives 

 its specific name from the possession at the hinder end of the body of 

 three cylindrical appendages, which are so set as to form with the body 

 the figui'e of a cross. 



Excretory Organs of the Trematoda and Cestoda. j — M. J. 

 Fraipont directs attention to some points, of which we have not 

 yet taken notice. In the lower forms the system is typically formed 

 of two longitudinal canals, which extend throughout the whole length 

 of the body, and either open to the exterior directly, or by the inter- 

 mediation of a vesicle with a single median orifice. These longitudinal 



* Overs. K. Danske Yidensk. Selsk. Forh., ISSl, pp. 52-84 (2 pis.), 

 t Bull. Soc. Belg. Micr., vii. (1S81) pp. xssi.-xlii. 



