138 MORPHOLOGY OF INVERTEBRATE TYPES 



in your left hand and looking into it from the back so that the 

 longitudinal axis of the body coincides with the axis of vision, 

 make a full size drawing showing the skeleton of the three 

 preoral segments. Label the articulation sockets of the eyes, 

 below them a more or less T-shaped sternite of the second seg- 

 ment separating the sockets of the first pair of antennae, and 

 behind this and forming together with it the epistome, the 

 sternite of the third segment. The lateral projections of this 

 sternite are hinged to the carapace and help to form the sockets 

 for the second pair of antennae. The two lobes in front of the 

 eye-sockets are the procephatic processes and serve for the at- 

 tachment of the anterior gastric muscles. The bridge between 

 them is supposedly the tergite of the first or ocular somite, 

 while the two sides of the oval containing the eye-sockets are 

 the epimeral plates of this segment. The thin bars separating 

 the socket of the first antenna from that of the second antenna 

 are the epimeral plates of the second somite. The thickened 

 edge of the carapace is formed by the epimeral plates of the third 

 somite. Attached to the base of the third sternite (and over- 

 hanging the mouth) is the upper lip. 



5. Remove all appendages beginning with the tail-fan and 

 proceeding gradually forward. In doing so cut the articulation 

 membrane with a sharp scalpel and label every appendage for 

 future use. The label should be tied to the appendage and 

 must show the number of the segment and the side of the body, 

 as for example, left fourteen. This is easily done because the 

 telson is the twenty-first segment. The gill-bearing appendages 

 should be removed with the gill attached to them. There are 

 altogether six pairs of these so-called podobranchiae, one pair 

 for each somite from the eighth to the thirteenth. When all 

 appendages have been removed, separate the abdominal seg- 

 ments by cutting the membrane between them, clean and label 

 each segment for future study. Put the cephalothorax into a 

 glass beaker half filled with a 5% solution of potassium hydrate 

 and boil it till all tissues will be dissolved except the endophrag- 



