GONIONEMUS MURBACHII Mayer 



Material. G. murbachii is common in a certain locality 

 in Woods Hole and may be obtained from the Biological Labora- 

 tory. Specimens for microscopic study should be preserved in 

 i% osmic acid. Every student should study a specimen pre- 

 served in formalin and the following prepared slides: a radial 

 section through the velum and bell edge, a cross-section of a 

 tentacle, a cross-section through the manubrium and a cross- 

 section through the peduncle. The general plan of structure 

 is so similar to that in Tima that a separate description is not 

 needed and the specific characters will be pointed out in the 

 instructions. 



Instructions 



i. Examine a specimen of Gonionemus in a stender dish with 

 water. To see it best turn it so that it shows more than its pro- 

 file, enabling you just to see the bell opening. Make a half 

 page drawing of it in this position. The drawing should show: 

 the almost hemispherical exumbrella, the powerful velum, the 

 bell cavity and the subumbrella; hanging down from the centre 

 of the subumbrella the short peduncle with the manubrium and 

 four lips surrounding the mouth; the four radial canals and 

 under them the sigmoid bands which are the gonads; the cir- 

 cular canal near the margin; the tentacles each with a swollen 

 base or bulb and thin shaft. (In a live specimen there is a bright 

 green pigment spot in the endoderm at the base of every tentacle, 

 but the color disappears in formalin.) In making the drawing 

 observe that the peduncle and manubrium have not the shape 

 of a square in a cross-section but that of a cross. The number 

 of tentacles varies in Gonionemus and depends largely upon the 



33 



