132 LILIAN SHELDON. 



prolongation (C.) of the ciliated pit in a way precisely similar 

 to that described by Julin. 



(2) In Amarsecium proliferum the ciliated pit (fig. 2, 

 C.P.) is shorter and simpler than in Clavellina. It consists of 

 a funnel, communicating by a circular opening with the 

 mouth, and is lined throughout by ciliated columnar cells. It 

 lies immediately ventral to the ganglion, with which it has 

 no communication. At its apex it opens (P.) into a mass of 

 spongy tissue (Ti.) lying ventral to it, which has a definite 

 boundary, but is not glandular in structure, appearing rather 

 to consist of degenerated tissue, somewhat resembling the 

 notochordal tissue of Vertebrate embryos. 



(3) Ascidia and Ciona. — I have examined several species 

 belonging to these genera, and have found that the condition 

 is similar to that described by Julin 1 in several species of 

 Corella, Phallusia, and Ascidia. The pit consists of a ciliated 

 funnel passing into a canal. A mass of glandular tissue lies 

 ventral to the canal and opens into it by a number of ducts. 

 The opening into the mouth is sometimes circular, but more 

 often horseshoe-shaped. 



(4) The condition in Phallusia mammillata has also 

 been described by Julin. 2 A large reservoir lies ventral to the 

 ganglion, ccmmunicating with the mouth by a comparatively 

 small orifice. A large number of small canals open into the 

 reservoirs and also communicate with the atrial cavity by a 

 number of secondary funnel-shaped openings. Round the 

 funnels are situated masses of cells of a deep yellow colour. 



Condition in the Embryo. 



Amarsecium Embryo. — The embryo remains in the atrial 

 cavity of the parent until it has attained to the fully-deve- 

 loped tadpole stage. 



The nervous system then consists of four parts : 



1 Julin, C, loc. cit. 



2 Julin, C, loc. cit., " Deuxieme Communication." 



