96 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



We are not prepared to say that the cell bodies at the end of the excretory processes arc 

 composed of two cells, but it. is a fact that two nuclei exist, and this conclusion is not based 

 on sections through bent nuclei which might lead one to think that there were two when only 

 one existed. It will be seen from this description that the anatomy of the excretory cells and 

 processes of the Actinotrochat which we have studied resembles that of similar structures 

 described by Goodrich for Amphioxus. 



There is nothing new to add concerning the nephridial canal except that a longitudinal 

 section through it, which has been stained with iron haematoxylin, shows long flagella extending 

 some distance from the distal end into its lumen (tig. 52;/). 



Sections of the Actmotrocha of Phoronis sabatieri show that the nephridia resemble those of 

 other Actinotrochse studied, although they do not seem to be as well developed as those of 

 Species A. and 15. The specimens at hand show that the internal opening in the collar cavity is 

 situated at about the same level as in other Actinotrochse and not at the level of the oesophagus, 

 as Koule (20) has indicated. 



The course which the canal takes is like that which has been described by other investigators, 

 and we agree with the observation of others in regard to the nephridial canal opening to the 

 exterior at the sides of the ventral pouch opening. 



Masterman (15) describes a pair of ciliated pores opening to the exterior on the dorsal surface 

 of the preoral lobe. These, he finds, lead into tubes closely similar in cross section to the cross 

 section of canals of the collar nephridia, and these tubes have an internal opening into the preoral 

 lobe cavity. He compares the external- pores to the proboscis pores of Cephalodiscus. In the 

 Zoologisher Anzeiger, 1901, Volume XXIV, page 231, he admits that their occurrence is variable. 

 No other investigators have found these organs. Ikeda mentions the fact that flask-shaped 

 glands on the upper fact 1 of the preoral lobe occur in one larva studied by him, but he denies 

 that they are such organs as Masterman describes. 



Masterman (15) also finds thin-walled organs lying in the hsemocoele space immediately below 

 the anal ciliated band. Speaking of these (15) he says: "A pair of organs which I have not fully 

 made out, but they may be the rudiments of the trunk nephridia." Masterman, however, denies 

 their existence in a later paper, and no one else has seen the organs, as far as we know. 



Rudiments of tht adult Hood vessels in tht Actinotrocha. Many investigators of Hh& Acti- 

 notrocha have recognized the beginnings of the adult blood vessels, but. E. B. Wilson (21) is the 

 first one who clearly states the fact that the cavity containing the blood corpuscle masses give- 

 rise to the ring vessel of the adult, 'although Metschnikoff seems to have had some such idea. 

 Caldwell (3) and Ikeda (!) confirm the statement of Wilson with reference to the origin of the 

 ring vessel of the adult. 



While Masterman (15) describes a much more complicated vascular system for the Actino- 

 trocha from St. Andrews Bay than that of all the Actinotrocha examined, yet we agree with 

 him in his view that the cavities of the blood vessels may be considered as vestiges of the 

 segmentation cavity. 



Above we have given our opinion that the "subneural sinus" (Masterman) does not exist in 

 the Actinotrochat that we have examined, and that although there is a space beneath the ganglion 

 it has no connection with the dorsal blood vessel. 



The blood vessels of the adult are represented in the A<tht<itr<ieh;i Species A. and H. by a 

 dorsal vessel (figs. 34, 35) extending along the median dorsal line of the intestine, from the 

 mesentery between the collar and trunk almost to the posterior end of the stomach, where there 

 are small csecal outpushings of the splanchnic mesodermal walls of the end of the stomach. This 

 dorsal blood vessel, although it is a completely formed vessel, has arisen from a proliferation of 

 the cells id' the splanchnic mesodermal wall along the dorsal median line of the stomach, and its 

 lumen is really a part of the blastoccele i. e., it is a part of the space between the splanchnic 

 mesodermal lining and the wall of the stomach. Posteriorly, the dorsal blood vessel becomes 

 indefinite and passes into the ordinary splanchnic mesodermal lining, thus really being open pos- 

 teriori}' into the space between the wall of the stomach and the mesodermal lining. 



