34 THE NAUTILUS. 



canals") of the charged marsupium of the Anodontinae as a 

 special device for aeration, not of the embryos, as I believe, 

 but of the blood of the gravid female, the mother. Their ar- 

 gument is, that it is hard to see that a canal shut off from the 

 embryos by a membrane could increase the facilities of aera- 

 tion. I think, this argument rests upon a complete misunder- 

 standing of the requirements and actual conditions; a canal, 

 which permits a circulation of water within the gill, although 

 separated from the embryos by a thin membrane, surely gives 

 a better chance for aeration of the embryos, than the complete 

 absence of such a canal, and, consequently, the complete ab- 

 sence of any water circulation within the marsupial gill. The 

 mass of embryos inside of the water tubes is of such a char- 

 acter, that it would completely choke up the ostia, and there 

 would be only a water current over the outer faces of the gill, 

 separated from the embryos by the whole thickness of the 

 gill-lamina, which is considerable. For this reason, I em- 

 phatically must maintain my first opinion, that the lateral 

 water tubes have the function of furnishing breathing water 

 for the embryos and glochidia, and not for the mother. 



(To be continued.) 



A. C. BILLUPS. 



Mr. A. C. Billups died early in June at his home in Law- 

 renceburg, Indiana. He was known to couchologists as an 

 ardent collector of shells, his chief interest being in fresh- 

 water species. Besides his conchological work, Mr. Billups 

 was known as an entomologist, a pursuit in which he took 

 especial delight and satisfaction. In his business as a mechan- 

 ical engineer, Mr. Billups traveled extensively for a time, in- 

 stalling power plants of various kinds; and this gave many 

 opportunities for collecting in those branches of natural his- 

 tory which interested him. It also gave opportunities for 

 personal intercourse with brother naturalists, many of whom 

 will hear of his death with sincere sorrow. Mr. Billups is sur- 

 vived by his wife and son, Mr. C. F. Billups. 



