SEA-PISHERIES LABOEATOitY. 29? 



study of the brain, nuchal organ, &c. ; and horizontal 

 sections are almost essential for the study of the nervous 

 system, particularly the brain, otocysts, the ventral nerve 

 cord, and the giant cells. If sections of certain organs 

 only be desired, it is best to procure these from a worm 

 chloroformed and opened as soon as it is taken from the 

 sand. The organs are excised, separately preserved and 

 sectioned as desired. The following parts may be sug- 

 gested — the otocyst, various portions of the alimentary 

 canal to show the condition of the gland cells, &c, when 

 the gut is full of sand (of course, the sand must be rapidly 

 washed out with sea water before preserving each part), a 

 nephridium with gonad,* and a heart (one not dilated with 

 blood, as when imbedded the blood becomes very brittle 

 and impossible to cut). 



Post-Larval Stages. 



These are not readily obtained. Occasionally living 

 specimens ma}* be got from Plymouth in March and April. 

 These are, of course, best for examination, as some of the 

 structures described, such as the processes on the nephro- 

 stomes, can only be seen in living specimens. Preserved 

 specimens should be lightly stained in borax carmine, and 

 examined in cedar-wood oil, so that they may be turned 

 over as occasion requires. For preparation of setse cut out 

 two or three of the posterior chsetigerous segmentst and 

 warm gently in a watch glass in 5 per cent, caustic soda. 

 Before the muscular tissue is dissolved transfer by means 

 of a pipette to water, and later to glycerine. After 



* Whole mounts of the first nephridium, and one or two others 

 with their gonads are very useful. Stain with carmine and mount in 

 balsam. 



t From a spirit specimen. If the specimen be in oil remove the 

 latter by treatment with absolute alcohol before warming in caustic 

 soda. 



