52 MORPHOLOGY OF INVERTEBRATE TYPES 



your fingers and cut it with large scissors in two a little below 

 the capitulum. The cut must be made at right angles to the 

 axis of the polyp in the same manner as you would cut across 

 rubber tubing. Put the two halves in separate finger bowls. If 

 the cut was not quite neat, trim the edges and mesenteries with 

 scissors, till you obtain a perfect cross-section. This method is 

 vastly superior to a cross-section made by a razor. Examine the 

 cut surface of the upper half. Make a half page drawing showing 

 gullet, siphonoglyphs, primary mesenteries with inner septo- 

 stomata, incomplete mesenteries, and between them the open- 

 ings leading into the tentacles, circular muscle. Label also 

 the one or two pairs of primary mesenteries which are the 

 directives. 



4. Take the lens from the dissecting microscope and examine 

 the cut surface of the gullet. Make a drawing showing the 

 three layers: ectoderm, mesoglcea, and endoderm. 



5. Examine the cut surface of the lower half. Make a half 

 page drawing showing primary mesenteries with their muscle- 

 banners, incomplete mesenteries, mesenteric filaments, gonads, 

 gullet with siphonoglyphs. Label also the directive mesenteries, 

 exocceles, and endocceles. 



6. Cut the lower half in the same manner as before, but this 

 time close to the foot. The cut should be below the gullet, but 

 if it happened to be above the end of the gullet, trim the sur- 

 face with scissors. Make a half page drawing showing primary 

 mesenteries, incomplete mesenteries, gonads, and acontia. 



7. Take another specimen. Introduce the blunt end of the 

 large scissors into the mouth and cut the specimen into two 

 symmetric halves. The cut must be made through the corners 

 of the mouth so that each siphonoglyph will be cut in two. 

 Put both halves in a finger bowl with water and choose the one 

 which has been less damaged. Trim the edge to the primary 

 mesenteries until you have a clean longitudinal section with the 

 gullet in the middle and a complete mesentery on each side of it. 

 Make a half page drawing showing capitulum with tentacles, 



