128 SYDNEY H. VINES. 



tremity of each^ which generally increases in size as the 

 cilium becomes shorter, and which finally coalesces with the 

 ectoplasm. 



The hyaline apex of the zoogonidium of Oedogonium, 

 which consists of ectoplasm and which bears a ring of cilia 

 on its posterior margin, give no indications of structure like 

 those found in Vaucheria, nor were any such indications to be 

 found in that part of the zoogonidium of Ulothrix which 

 bears the four cilia. From these facts Professor Strasburger 

 concludes that the above-described structure of the ectoplasm 

 and its relation to the cilia in the zoogonidia of Vaucheria,. 

 is a special adaptation, though the occurrence of a radial 

 striation in other places suggests that this special adaptation 

 has been favoured by the molecular structure of ectoplasm 

 in general. 



Numerous examples of a striation of the ectoplasm might 

 be drawn from the domain of animal histology. Of these 

 Professor Strasburger avails himself of a few only. He 

 recalls the observation of Ed. van Beneden, that the eggs 

 of star-fishes present a striated outer layer which occupies 

 nearly a third of the radius of tfie yolk, and he points 

 out the similarity which exists between the " exoplasma " 

 (Haeckel) of many Infusoria with its trichocyst layer, and 

 the ectoplasm of the zoogonidium of Vaucheria with its rods. 

 It must be remembered, however, that all observations tend 

 to show that there is no connection between the trichocysts 

 of Infusoria and their cilia. 



It has already been mentioned that the plasmodia of the 

 Myxomycetes are differentiated into an ecto- and an endo- 

 plasm, and de Bary, Hofmeister, and Kiihne have men- 

 tioned the radial striation of the ectoplasm in their accounts 

 of these organisms. Professor Strasburger has been able to 

 confirm their observation, and to add a complete account of 

 the manner in which the pseudopodial processes are thrown 

 out and retracted (Figs. 4 and 5). 



The ectoplasm is distinguished from the endoplasm not 

 only by its structure but also by its properties. Close ob- 

 servation of the zoogonidia showed that, after a period of 

 active movement, a cellulose envelope begins to be formed 

 at the surface, and this Professor Strasburger regards as the 

 cause of the cessation of movement. He finds that if such 

 a body be pressed, so as to cause the extrusion of part of its 

 endoplasm, no cellulose envelope is developed around the 

 masses thus set free. If water be added to the zoogonidium, 

 which has thus been deprived of part of its substance, the 

 ectoplasm contracts away from the cell-wall to which it was 



