April 16, 1897.] 



SCmNGE. 



629 



SOCIETIES AND ACADEMIES. 



BIOLOGICAL SOCIETY OF WASHINGTON — 273D 



MEETING, SATURDAY, MARCH 13. 



A PAPER by R. T. Hill and T. W. Vaughn 

 on ' The Lower Cretaceous Gryphseas of the 

 Texas Region ' was presented by Mr. Vaughn. 

 He spoke of the abundance of the individuals 

 of this genus and their value in determining 

 the location of artesian wells, the various species 

 being characteristic of certain strata. He traced 

 the phylogeny of the species and dwelt at some 

 length on their involved synonymy. 



Chas. F. Dawson spoke of the ' Dissemination 

 of Infectious Diseases by Insects,' instancing 

 the manner in which tuberculosis, swine plague, 

 Texas fever and anthrax could be thus spread. 

 The speaker described his own experience with 

 flies, stating that from their habits they were 

 particularly liable to convey disease. 



Under the title, ' The Type (?) of a New-Old 

 Species, ' William Palmer spoke of the confusion 

 which existed in regard to certain genus of 

 birds, stating that while Linneeus had originally 

 given a specific name to what he believed to 

 be a cosmopolitan species, he had subsequently 

 admitted a second species, based on a plate, 

 while another author had described a third from 

 still another plate. There was no type existing 

 of any of these, while the authors of the 

 second and third species had no specimens when 

 they established their names. Mr. Palmer 

 stated that two distinct birds had been confused 

 under the three names, and that he proposed 

 to separate them, basing his description on a 

 bird which he had selected among numerous 

 specimens. Would this specimen, to which a 

 binomial name and definite description were 

 attached for the first time, be a type ? 



Sylvester D. Judd, in a paper entitled ' Sex- 

 ual Dimorphism in Crustacea,' limited himself 

 to the Amphipoda. He stated that while in 

 certain genera the males and females were very 

 similar, there were other genera where second- 

 ary sexual characters were so marked that 

 different sexes of the same species might be 

 thought by the casual observer to belong to dif- 

 ferent genera. The anterior and posterior parts 

 of Amphipoda are the parts that present sec- 

 ondary sexual characters. The antennae are 

 particularly subject to variation ; in some 



species the inferior antenna is several times as 

 long in the male as it is in the female. In 

 other species the caudal end of the body of the 

 male is monstrously developed. The hairs that 

 occur on the anterior and posterior parts of the 

 body are differently disposed, thus only in the 

 males of Byhlis do the antennal hairs form 

 brushlike tufts, and in a number of other genera 

 the hairs on the antennae of the males are modi- 

 fied into elaborate sense organs called calceoli. 

 It appears that the parts of the body of Amphip- 

 oda which exhibit secondary sexual characters 

 often coincide with those parts upon which 

 specific differentiae are founded. 



F. A. Lucas, 

 Secretary. 



ZOOLOGICAL CLUB, UNIVERSITY OF CHICAGO, 

 MEETING MARCH 4. 



I. Cleavage of the Egg of Arenicola. The 

 cleavage belongs to the type known as ' spiral,' 

 or better oblique. There is considerable yolk 

 in the egg and it is almost evenly distributed 

 before segmentation. In the four-cell stage 

 there are three smaller cells and one very large 

 one representing nearly half the entire egg. 

 All the cells contain yolk. The two ' cross- 

 furrows ' on the upper and lower poles of the 

 egg are parallel and are formed by the blasto- 

 meres B and D ; the cross-fiirrow at the lower 

 pole is much longer than the other, however, 

 and is perfectly constant up to a stage shortly 

 before the closure of the blastopore, thus afford- 

 ing an invaluable means of orientation. The 

 future median plane passes at right angles to 

 this furrow and thus forms an angle of 45° with 

 each of the first two cleavage planes. The 

 upper pole forms the anterior end and the lower 

 pole the posterior end of the worm. 



Ectoblasts, mesoblasts and entoblasts are 

 formed in the usual way. The cells X and M 

 (vid. Wilson, Nereis) are by far the largest 

 cells in the egg. Primary trochoblasts, sixteen 

 in number, arise from first quartet and are 

 supplemented later by three cells from each of 

 the small micromeres of the second quartet, 

 which complete the prototroch except dorsally, 

 where a break is left. Through this space four 

 cells, derivatives of the first quartet, pass and 

 come to lie posteriorly to the pototroch. The 



