STRUCTURE AND DEVELOPMENT OF COEEOPT,.\NA. u 



the meridional canals, the ovary (ovy) as a continuous tract of egg-cells 

 and the spermary (U) as a series of certain numbers of compact sperm- 

 cell masses. 



Not infrequently there are met with anomalous individuals in which 

 the two body halves on either side of the sagittal plane are quite 

 unequal 1}^ developed as regards both the external shape and the 

 internal structure. Indeed, it may be said to be rather exceptional 

 when those two body halves are perfectly symmetrically developed. 

 MoRTENSEN ('i2) has made a similar observation in Tjalfiella and has 

 regarded the asymmetry to be due to an incomplete regeneration of 

 parts lost by accidental damage. In this I fully agree with him. 

 Unfortunately, I could not ascertain how and to what extent regeneration 

 takes place in Coeloplana. But according to Krempf ('20, '21), even a 

 very small piece of the body can grow into a perfect individual provided 

 the piece possesses both ectoderm and endoderm. 



Epidermis. 



The epidermis of Coeloplana is in structure essentially ctenophoran. 

 It is in a highly differentiated state and consists, as in all ordinary 

 ctenophores, of gland cells and interstitial cells. The former are dis- 

 tinguishable into two kinds, the granular and the clear. 



On the dorsal surface of the body (PI. 4, fig. i), the epidermis 

 may be said to be made up very largely of the gland cells {c. g., g. g). 

 These are arranged very close together, restricting the occurrence of the 

 interstitial cells, so that these are found mostly in the deepest parts of 

 the epidermis {i. c). The two kinds of gland cells occur in about equal 

 frequency in the dorsal epidermis. 



The granular cells (" Kornerzelle ", Chun, '80; " Driisenzelle ", 

 Hertwig, '80;? " Drusige Deckzelle ", Schneider, '02; "Stadium C, " 

 Samassa, '92) (g. g) are generally broadly columnar in shape and not 

 of a swollen appearance. The cell-body includes in the distal parts a 

 crowd of spherules, while the basal parts may remain in a clear and 

 homogeneous state. The spherules measure 2-3 fJi in diameter and are 

 polygonal in form as the result of mutual pressure. They exhibit strong 

 affinity for eosin; they also take up deeply certain other dyes, such as, 

 acid fuchsin and orange G, as well as iron-haematoxylin. The basal 

 part of the cells often presents a basophilous reaction. 



The clear gland cells (" Glanzzelle ", Chun, 'So; " Deckzelle ", 



