70 



that all these substances actually penetrated into the radial sacs. 

 Since the animals did not take any food voluntarily, I had to 

 feed them artificially. The animal was laid down on the table 

 with its mouth turned upwards. The needle of an injection 

 syringe was now introduced into its stomach. As the animals 

 on such rough mechanical treatment frequently withdraw their 

 oral sphincter, I was often obliged to remove some of the 

 spines surrounding the oral cavity. The fluid was then injected, 

 in some experiments the animal was put into the water 

 again soon after the injection, sometimes the mouth was closed 

 with recently melted paraffin of a low melting point. The 

 animal frequently succeeded in soon getting rid of the piece of 

 paraffin, but yet, the paraffin did prevent the immediate squeezing 

 out of the injected substances. 



In some of these experiments the animals autotomised their 

 arms, probably on account of the unusual stimulation by injec- 

 tion and unnatural food. This peculiar autotomy takes place in 

 starfishes along the interradial saepta which divide the coelom 

 of the disc in five parts. It takes place very easily in some 

 species; Luidia ciliaris, according to Cuenot 22), is almost never 

 caught in intact condition. They are like folds projecting 

 inwards from the interradial spaces ; they are stiffened by a calca- 

 reous deposit and are the areas of lateral adhesion of the arms. 

 In them the stone-canal and the axial sinus are found. If all the 

 arms are removed in this way, only an exceedingly small part 

 of the disc is left as central part. 



It needs not to be stated that ..abnormal" animals of this 

 kind were always excluded. 



One of the injected substances was the saccharate of iron. 

 This substance has frequently been used in experiments on 

 resorption, on account of the fact that it is so very easy 

 to make iron visible in microscopical sections. As examples from 

 invertebrate physiology, I might quote the papers of Jordan 69) 

 on the resorptive function of the middle-gut gland of Helix 

 pomatia and that of S t e u d e 1 1 23) on absorption and secretion 

 in the gut of insects. 



The substance was prepared according to the U. S. Pharma- 

 copea (carbonas ferrosum saccharatum). In injecting such prepara- 

 tions one must be very careful to use a very small dosis, since 

 even traces of iron are toxic (see also Jordan 63)). A very 

 dilute solution of the preparation was used for this reason, which 

 has a light brown color. 



At different intervals after the injection, the animals were 

 opened, inspected and, if they looked promising, the radial sacs were 

 fixed. It was most interesting to observe how the material entered 

 the radial sacs through the ducts. The small iron particles which 

 had not gone into solution could clearly be seen through the wall 

 of the ducts and eventually one could even see them move. 



