104 University of California Publications in Zoology [VOL. 13 



That neither his description of the anatomy nor his interpretation 

 of the function of the ' ' Stiitzapparat " of Ophryoscolex purkynjei 

 will hold, even in the main, for the skeletal structure of Diplodinium 

 ecaudatum may easily be seen from a glance at the microphotographs 

 (pi. 7, figs. 20-33). 



Braune (1913, pp. 152-154, and pis. 6, figs. 38-40) states in the 

 first place that the "Stiitzapparat" is a unit organization, a struc- 

 ture ("einheitliches Gebilde") situated in the "Entoplasma a," and 

 filling the entire ventral side. Microphotographs 23-29, plate 7, show 

 very clearly that for D. ecaudatum the skeletal structure is much 

 more complicated, that it consists of three component parts, well de- 

 fined at the anterior end (figs. 25-26) and merging near the middle 

 of the animal (figs. 28-29) ; that these component parts are situated 

 in the ectoplasm, and that at the anterior end of the animal this 

 structure extends over the entire ventral half of the circumference 

 of the body, but as the posterior half of the body is approached the 

 structure comes to lie more and more to the right side. 



A second point made by Braune is that the "Stiitzapparat" is a 

 plate with its lateral edges bent in towards the inner part of the body 

 and its anterior ends drawn out to points thus better to surround the 

 oesophagus. An examination of the microphotographs 22-29, plate 

 7, shows conclusively that in the case of D. ecaudatum the skeletal 

 structure cannot be described as a plate with its lateral edges bent 

 in towards the inner part of the body nor are the anterior ends drawn 

 out to points, for it will be noted that figure 23, plate 7. which repre- 

 sents the fifth section in the series, and one which is the most anterior 

 section showing this skeletal structure, gives absolute evidence, by 

 measurement, that each of the three component parts is actually broader 

 at its most anterior extremity than at any other level in its^ entire 

 length. Also in these first five or six sections which represent the 

 anterior one fourth of the animal it is plainly evident that the 

 oesophagus has no definite connection with the skeletal structure 

 other than with the surrounding ectoplasm. 



In the third place Braune maintains that this structure may be 

 divided into three layers, (a) an outer layer composed of fine, long, 

 interlacing fibrillae, (b) a middle, alveolar layer (described by 

 Giinther, 1899, 1900), composed of very large alveoli which at times 

 occupy the whole thickness of the supporting structure, and (c) an 

 inner " Fibrillenlage " situated between "Entoplasma a" and "Ento- 

 plasma b" which exhibits the large, parallel fibrillae. Again exam- 



