284 



THE AMERICAN NATURALIST [\^ol. XLI 



The Conus Arteriosus in Teleosts. — One of the characters which 

 have been relied upon to distinguish Ganoids from Teleosts has been 

 the presence in all (xanoids and, with the exception of Butirinus, 

 its absence from all of the other group. H. 1). Senior now shoAvs^ 

 that the tarpon of our southern waters has a conus with two rows 



Does half of an Ascidian Egg give rise to a whole Larva? — In 



reply to criticisms of Dricscli, Conklin n-tuni. t.. tlii. (jucstion which 

 was' discussed in his earlier i)apers and maintains (Archiv f. Entwick- 

 lin.gsnKvliai.ik, 21, 19()(.)) the general correctness of his former account. 

 The hair l)lastomere cleaves as if it were still part of the entire egg; 

 (•(u-rcspoiidingly the resulting gastruUe are half gastruhe and are in 

 no wise l)ilaterally symmetrical and the anlagen of muscles and 

 mesenchyman unilateral in position. Similarly the larvfe uj) to the 

 time of metamorphosis are half larvie, having only the parts belonging 

 to one side — right or left — represented. They "are such as would 

 result if a fully formed larva were cut in the median plane and the 

 cut edges of each half then came together, the dorsal and ventral 

 mid-lines joining. These results follow from the early differentia- 

 Digestive processes in Collembola. Dr. .1. W. 1m)1s()iii and Miss 



TonHH-rn,. .nd m h.,' '( ■o'iKmmI. 'la TlL <|rnv the rxis,.,uv of 

 Malpio-hian tnlxil.- in thcr inM-ci. :,nd .u.lr th,- lad that thry molt 



tion of the intier half ..f the intestinal epithelium, the (legcnerate 

 portion being ca^t out soon after the molt, .•arrvino- with it a part of 

 the nuclei wiiieli aiv n-plaee,l mit.»tieally from those- which persist. 

 In this degeneratinu- mas> is containeil xxlic urate as well as gre- 

 garine so that this is an exen-torv process. Adult specimens molt 

 everA- six or <-ii:ht day>: the cast skin i. dev.Mired. 



Fresh Water Amphipods of North America. Miss Ada Weekel 



