COELENTERATA 



19 



ring removed do not show spontaneous movements because insensi- 

 tive to other than strong stimuli. 



Coordination is not dependent upon the function of any nerve 

 center, but upon the rapid transmission of an impulse. 



Krasinska finds fibrillae within the ganglion cells of hydroid 

 medusae by means of the iron-hematoxylin method. 



In Poiijorchis, Little 1914, there are two nerve rings, the lower 

 being the larger. All the cells are bipolar. Connections between 

 nerve cells and eye were not determined. 



Work by Romanes '98 shows nervous connection between the 

 tentacles and also the manubrium. 



The sense organs of medusae, marginal octocysts and eye spots 



Fig. 6. A. Nerve cells from nerve rings of Gonionemus, Hyde. B. Eye spot 

 above lithocyst below tentacle base, medusa. C. Eye spot at base of a 

 tentacle of a hydroid jellyfish, Little. D. Tentaculocysts hydroid 

 medusa, Mayer. E. Tentaculocyst hydroid medusa. Haeckel. F. Ten 

 taculocysts from Trachimedusae, Mayer. G. Tentaculocyst hydroid 

 medusa, Haeckel. H. Section through sense organs, eye spots and 

 otolith of scyphozoan jellyfish. I. and J. Front and side views of 

 scyphozoan jellyfish sense organ. K. Simple eye of medusa Schewai- 

 koff. L, Section through more complex eyes of Anrelia. M. Marginal 

 notch and tentacle of AnrcIia from above. Eimer. N. Section through 

 marginal tentaculocyst of scyphozoan showing sense areas, dark. 

 O. Section through tentaculocyst scyphozoan, Hesse. 

 E., from Dahlgren and Kepner's Histology. G., M. and N., from Parker and 



Haswell Zoologv, permission of Macmillan Co. 



