. MUSEUM OF COMPARATIVE ZOOLOGY. 11 



He further says, "The substance of the epidermis is probably made up, 

 in the living condition, of cells resembling the gland-cells described, but 

 of various dimensions, and of cells containing rod-like bodies." 



Since the " rod-like bodies," or rhabditi, are really modified glands, 

 Moseley's statement amounts to saying that the epidermis is composed 

 entirely of gland cells, a conclusion which it is not easy to adopt. More- 

 over, I believe that Moseley's "gland-cells" are only rhabditi that have 

 been modified by the action of the reagent which he used for their 

 demonstration. Kennel ('79, p. 126) obtained similar conditions by the 

 action of chromic and acetic acids on the rhabditi of land planarians. I 

 have found that in Phagocata by the use of picric acid the dermal rods 

 become swollen and granular, resembling the "gland-cells" described 

 and figured by Moseley. " The vertical filaments " were undoubtedly 

 the true epidermal cells, reduced to a filamentous condition by the 

 influence of the many rhabditi lying between them. 



I cannot find any organic connection between the cells of the hypo- 

 dermis and the deeper tissues, such as has been described by lijima. 

 Although appearances like those described by him do occur, they are 

 secondary conditions, dependent on the presence of the rhabditi and the 

 development of their mother cells. The basement membrane is every- 

 where traversed by fine tubular processes of the mother cells of the 

 rhabditi, which lie imbedded in the body parenchyma. This fact, 

 together with striations of the cells of the hypodermis and the ultimate 

 reduction of these cells to filaments, might easily lead to conclusions 

 such as those of lijima. His sections were thick (10-20//,) both abso- 

 lutely and in proportion to the length of his largest specimens (20 mm.), 

 whereas my sections were only 5-10 /t in thickness, although the worm 

 attains the length of 35 mm. ; moreover, isolation preparations were 

 studied in connection with these sections. 



The hypodermis consists of the hypodermal cells and the rhabditi 

 that lie between them. There are no unicellular glands in it. Lang 

 ('84, p. 49) described in Polyclads a granular " interstitial tissue " con- 

 taining nuclei and pigment which arises, according to his conjecture, 

 from a coalescence of indifferent epithelial cells. Such conditions I 

 cannot find, nor can I detect any cement (" Kittsubstance "), such as 

 that described by Graff ('82, p. 44) for Rhabdocoeles. 



The dermal rods or rhabditi are defined by Graff ('82, p. 49) as "die 

 stark lichtbrechende glasartige homogenen Stabchen, welche weder 

 einen Faden noch einen Nadel einschliessen und durch ihre glatte Ober- 

 flache, regelmassige Gestalt und ihren Glanz auffallen." 



