Zool.— Vol. I.] BANCROFT— CHELYOSOMA PRODUCTUM. 319 



places. Nor are these ampullce confined to the terminations 

 of the blood-vessels, for one or even several pairs of 

 blood-vessels may enter the cavity from a proximal direc- 

 tion and another pair leave it distally to unite again in some 

 terminal ampulla. 



Union of Muscles and Test. 



Both Eschricht (1842) and Drasche describe the intimate 

 connection between the muscles and the test, especially in 

 the region of the siphonal ridges ; but so far as I know no 

 one has described the means by which this union is accom- 

 plished. Wherever a bundle of muscle fibres is attached 

 to the test the latter is produced into a conical or ridge-like 

 papilla to the summit of which the muscles are joined. 

 This attachment is accomplished principally through the 

 intermediation of the ectoderm. The cells of this layer 

 usually form a cubical or thin pavement epithelium which 

 may become vacuolated and very irregular in places, but 

 on the test papillae the epithelium is always of the columnar 

 form (figs. 6 and 11) and is more actively engaged in 

 secreting cellulose. The increased activity in this region 

 is proved by the presence of the test papilla which can 

 hardly be explained except as the result of this activity, by 

 the larger number and size of the ectoderm cells, and by 

 the pronounced character of the processes that extend from 

 them into the test. These processes have been found by 

 Seeliger (1893, p. 494), Ritter (1893, p. 55), and others, 

 who think that they are in some way connected with the 

 active secretion of cellulose. In addition to subserving this 

 function they insure a firmer union between the test and 

 the ectoderm, but these two layers are nevertheless sepa- 

 rated by the strong contractions of the animal. In fig. 10, 

 a and d, this separation and the processes that have been 

 torn out of the test are shown. In the adjacent sections of 

 this series they are considerably more numerous, and the 

 columnar cells more closely packed together. On the sum- 



