April !•_>, 1895.] 



SCIENCE. 



419 



edge of relationships. Numerous cases 

 were cited showing such variation. In 

 Unto novi-eboraci the branchiae are some- 

 times free only a short distance on the 

 posterior part of the abdominal sac ; in 

 other cases they are united the whole 

 length, and the same is found to be true to 

 a great extent in U. mtdfijAicatus. In that 

 species and some others not closely related 

 the embrj-os are found in all four leaves of 

 the branchiae but in all other Jforth Amer- 

 ican forms thej' onlj- occupy the outer 

 leaves. 



The statement was made that the dissec- 

 tion of a single animal of a widely dis- 

 tributed and variable species will probably 

 not give any more knowledge of all its 

 characters than the examination of a single 

 shell, Cadalia, Castalina and Glabaris, South 

 American Naiads, may either have no 

 siphons at all, or have them perfectly de- 

 veloped, and this variation occurs in the 

 same species. The families L'nionida: and 

 MutiUdw were founded on the absence or 

 presence of this character. In a new ar- 

 rangement of the Naiads v. Ihering has 

 based the family Unionkke on the fact that 

 the embrj'o is a glochidium. in which the soft 

 parts are enclosed in a bivalve shell, and 

 the Middidce was established on the fact that 

 the embryo is a lasidium, divided into three 

 parts, the middle one only being protected 

 by a single shell. 



Basing a classification on these characters 

 it will be found that the genera of the unionidce 

 have invariably heterodont teeth, or vediges of 

 them, while in the mutilidce the arrangement is 

 es$eniiaUy ta.radont. 



It is claimed that similar circumstances 

 of environment maj' produce like characters 

 of unrelated forms; the Mycetopus of South 

 America and Solenaia of China are bur- 

 rowers, and though belonging to different 

 families closely resemble each other in the 

 elongated shell and greatlj' developed foot, 

 and have both been placed in one genus on 



this account. Anodonta angulata burrows 

 in rapid streams and differs greatlj' in ap- 

 pearance from A. dejecta, which is closely 

 related but Uves in stagnant water. The 

 two were showTi to have affinities bj' con- 

 necting forms. 



Dr. Stiles spoke* ' On the Presence of 

 Adult Cestodes in Hogs.' He called atten- 

 tion to the remarkable fact that no adult 

 tapeworms were described as regular in- 

 habitants of Sus, and discussed the cases 

 recently mentioned by Cholochowsky in 

 Kussia and two cases wliich had recently 

 been reported to him from Iowa. One of 

 the Iowa cases was certainly a case of 

 chance parasitism in this host, and although 

 there are no satisfactory data upon which 

 to base an opinion concerning the other 

 cases, he thought helminthologists in gen- 

 eral would not admit the forms mentioned 

 to the lists of the parasites of hogs. 



Mr. Coville laid before the society a copy 

 of the newl}' published list of ferns and 

 flowering plants of the northeastern United 

 States, prepared by a committee of the 

 Botanical Club, A. A. A. S., in accordance 

 with the nomenclature rules adopted by 

 the Club, and gave a brief history of the 

 recent nomenclature reform in botany. He 

 jjointed out the fact that in a recent criticism 

 of the List by Dr. B. L. Robinson, who rep- 

 resents those still favoring the old sj'stem, 

 only a single specific point of vital principle 

 in the new sj'stem was really discussed, the 

 other items of criticism referring to details 

 which do not involve the principles them- 

 selves. Mr. Coville pointed out that in 

 view of the success of the new system as 

 ah-eady tried by several of our leading bot- 

 anical institutions and as tested for many 

 j'ears past in other branches of biological 

 science, together with the prevailing dis- 

 satisfaction regarding the old system among 

 working botanists, the new code gives eveiy 



*Notes on Parasites, 34 ; Centralbl. f. Bakt., u. Par. 

 1895. 



