524 MAYNARD M. METCALF, 



In Fig. 42 are shown the chief organs of the anterior end of the 

 pharynx as seen from the inside. Although not strictly connected 

 with the subject in hand, I wish to call attention to two blood sinuses, 

 one on each side of the base of the branchial siphon, right and left 

 {x of Fig. 42). These spaces are filled with a great mass of large 

 granular cells exactly resembling in their histological character the 

 cells of the phosphorescent organs of SaljM and Pyrosoma. As the 

 phosphorescent organs in Pyrosoma have the same position and are 

 likewise blood sinuses filled with large granular cells (probably modified 

 leucocytes) I believe we have, in Polycyclus, organs homologous with 

 the phosphorescent organs of Pyrosoma. Their appearance indicates 

 that they are probably functional as light-producing organs, but I 

 know of no observations upon the living Polycyclus to indicate that 

 this is so 1). Similar cells in a very difierent position have been 

 described in Boltenia reniformis (see page 512). 



The Botryllidae in general. 



The three genera I have studied agree very closely with one 

 another in the character of their intersiphonal organs. They are 

 similar in the simple funnel shape of the dorsal tubercle; in the 

 dorsal position of the gland; in the divison of the gland into two 

 portions, one a spindle-shaped anterior chamber, more or less filled 

 with cells in process of degeneration to form the secretion, the other 

 a posterior solid mass of cells united to the back of the ganglion; in 

 the presence of a slightly gangliated rapheal nerve; and in the ab- 

 sence of any rapheal duct. 



Polycyclus differs from Botryllus and Botrylloides in the peculiar 

 character of the cells of the solid posterior part of its neural gland. 



1) Herdman figures and describes two evidently homologous masses 

 of cells in Polycyclus jeffreysi Herdm., saying of them in one place: 

 ". . . . there are two opaque white spots placed one in the middle of 

 each side between the "oral" sphincter and the peripharyngeal band". 

 (Report upon the Challenger Tunicata, Part 2, p. 67.) Again he says 

 (p. 08): "Two rounded masses of yellowish green pigment cells are 

 found at the sides of the peribranchial zone, one immediately posterior 

 to each median lateral tentacle (tab. 4, fig. 10 pig). These are the 

 two opaque spots seen in the surface view of the colony. Similar 

 celhilar masses are found in the same position in PyrosomaJ^ In 

 Part 3 (p. 22) of the same work Herdman recognizes the phosphor- 

 escent nature of these cell masses in Pyrosoma. 



