90 



BIOLOGICAL LECTURES. 



weak solution of malic acid into a very fine pipette, and holds 

 this into a dish where fern spermatozoa are swimming, in a short 

 time all the spermatozoa will gather around the end of the 

 pipette, and even enter the latter. If, on the other hand, a 

 strong solution of malic acid is used, the effect is the contrary. 

 All the fern spermatozoa will try to get away as far as possible 

 from the now poisonous substance. If we assume that the 

 basic secretion or waste product of the funnel cells has in a 

 very weak solution a positive chemotropic effect upon the 

 excretophores, it is certain that the cells which come under the 

 influence of the basic fluid will stream towards the point of 

 origin of this substance. In the neighborhood of the funnel 

 the concentration will be greatest, and it is probable, even cer- 

 tain, that the strong base will have a fatal effect upon the cell 

 plasm. The excretophores would retreat if they were not hin- 

 dered by fresh masses of excretophores pushing forward. In 

 the extreme neighborhood of the funnel the destroying effect 

 of the base now takes place. The cytoplasmic threads are dis- 

 solved, the cohesion of the cell is destroyed, the isolating oil 

 drops form soapy substances with the base, and the excretory 

 granules become liberated. I have seen this latter process in 

 the living tissue. Having succeeded by careful dissection in 

 isolating funnels from the body without injuring them, I was 

 enabled to observe them living, their cilia being in rapid motion 

 for hours. (One funnel is about the size of ^ of a millimeter.) 

 During the process of dissection a great number of excreto- 

 phores were injured and destroyed, and the excretory drops 

 floated freely in the water. As soon as a group of these drops 

 came into close proximity of the funnel I noticed that the indi- 

 vidual drops swelled and became transparent, that neighboring 

 drops flowed together and thus formed great colorless drops 

 {d), in the middle of which the small excretory granules were 

 suspended. Finally, the drops mixed with the surrounding 

 medium, and the granules {e) were freed. This process I have 

 illustrated in Fig. 3. 



Before answering the following questions I have a few words 

 to say about the anatomical structure of the funnel and the 

 nephridium. The funnel apparatus consists of two distinct 



