18 BULLETIN OF THE 



gonopore and at the edges of the body. Another proof consists in 

 the fact that the reaction with stains is always the same for both 

 glands and rhabditi. With picrocarmine the effect is most striking. 

 All the tissues of the body take the carmine except the rhabditi and 

 the glands, both of which, owing to their yellow color, stand out in 

 contrast to the rest of the body. 



Keferstein ('68, p. 15) was the first to speak of the rhabditi as gland- 

 ular secretions, and he called the parent cells " Stabchendriisen," and 

 the rods "geformte Schleimmassen." More recently this view has been 

 confirmed by Lang ('84, p. 52) and Kennel ('88, p. 474). The secre- 

 tions both of the slime glands and of the accessory sexual glands often 

 appear as rod-shaped bodies, and it was evidently this appearance of 

 the secretions occurring around the sexual organs that led Jensen ('78, 

 p. 11) to consider them rhabditi, and to speak of them as urticating 

 organs functional during copulation, — the theory first suggested by 

 Anton Schneider. Similar rod-shaped secretions are figured by Graff, 

 who calls them " Schleimpropfchen." 



If we are to consider the parent cells as glands, what part do the 

 rhabditi play in the economy of the worm 1 I must agree w;ith Kennel, 

 that the rhabditi are of use to the worm in securing food, and, 1 may 

 add, serve also for protection. Phagocata, like all planarians, is car- 

 nivorous, and observation of its feeding habits has shown me that rhab- 

 diti are cast out of the body in large numbers, and that this condensed 

 secretion helps to entangle and disable the prey. If one of the worms 

 be placed on a glass plate with a very little water, it soon becomes 

 hopelessly entangled in its own secretions, and when in this condition 

 placed in abundant water, some minutes elapse before it can free itself 

 and regain its activity. If some of the slime be examined with high 

 powers of the microscope, it will be seen to contain many rhabditi, in 

 all stages of dissolution. The rhabditi dissolve slowly in water, and it 

 is by reason of this slow disintegration that the slime retains a thickness 

 and tenacity that impedes the movements of an organism in contact with 

 it long enough for the worm to lay hold of it with its many pharynges. 



The conditions found in parasitic Turbellarians ma}' be mentioned as 

 evidence that this is the function of the rhabditi. Only four parasitic 

 species have been studied histologically, three of which belong to the 

 Ehabdocceles and one to the Triclads. In all of these forms rhabditi 

 are absent, but in their stead are found sub-hypodermal glands which 

 resemble the parent cells of rhabditi, and like them open to the exte- 

 rior, — another illustration of the complementary occurrence of rhabditi 

 and glands. 



