1885.] Mr W. JBateson, Excretory system in Enteropneusta. 225 



numerous small spores, each provided with cilia. On this account, 

 and recalling the similarity of the Laminarias to the Fucaceae 

 rather than to the Florideae, it appears to him probable that the 

 so-called tetrasporangium containing four tetraspores is really a 

 four-oosphered oogenium similar to the like structures occurring 

 in certain of the Fucaceae, and that the sporangium discovered by 

 himself is an antheridium containing antheroyoids. Thus here a 

 sexual process is present which he believes also occurs generally 

 in the Laminarias. A striking confirmation of this theory has 

 been afforded by the phenomena occurring in the life-history of 

 D' Urvillea utilis. 



(4) On the types of excretory system found in the Entero- 

 pneusta. By W. Bateson, B.A. 



The author described the development of the so-called "heart" 

 of the Enteropneusta as a segregation of cells from the posterior 

 wall of the anterior mesoblastic pouch, dorsal to the notochord. 

 Between this structure and the notochord the true heart arises as 

 a mesoblastic split. It gives off a plexus of vessels which are 

 covered by conical cells, attached by their apices, in which the 

 nuclei occur. These cells are similar in character to those lining 

 the so-called "heart." The vascular plexus is differently arranged in 

 different species. In Balanoglossus Kowalevskii the capillaries are 

 irregular and anastomosing, while in B. salmoneus they are parallel 

 and do not anastomose. In the plexus in B. Brooksii (new species) 

 the condition is intermediate. An epiblastic ciliated sac is then 

 formed in the skin on the left side of the proboscis stalk. After 

 a time this sac communicates with the exterior and with the 

 anterior body-cavity. It was suggested that this pore is excretory; 

 and that certain yellowish-brown bodies found in and around the 

 glandular cells are conveyed to the exterior by it. 



A similar suggestion was offered as to the function of the two 

 ciliated pores which open from the second body-cavity to the 

 atrium. These pores arise as perforations through the outer wall 

 of the atrium. In the second body-cavity brown bodies are found, 

 similar to those in the proboscis-cavity, which are possibly carried 

 out by these pores. 



No evidence could be obtained of any currents flowing inwards 

 at any of these pores. 



