BDELLOURA OR SYNCOELIDIUM 69 



vascular tubules. These tubules are more easily seen in 

 specimens that have been under the coverslip some time. 

 The region anterior to the cerebral ganglia is a favorable 

 place. They form a clear, branching tracery, a little lighter 

 than the surrounding tissue. The flicker of the flame cells 

 can usually be seen, but they may be more easily seen in 

 Crossobothrium. Examine chart and textbook figures of the 

 water- vascular system. 



Make a good-sized drawing of a worm, showing the above 

 points. 



Reproductive Organs. — Turbellarian worms are hermaph- 

 roditic. In this form the various organs are so crowded to- 

 gether that it will be best to follow each system separately. 

 Compress a specimen under the slip and find the male or- 

 gans as follows: 



(a) The testes are the numerous rounded masses between 

 the lateral branches of the gut. They are connected by means 

 of fine tubes which cannot be seen in fresh specimens. 



(6) The vasa defer entia, two large tubes, one on either 

 side of the pharynx, which unite posteriorly near the base of 

 the penis. 



(c) The genital atrium, within which the penis lies with- 

 drawn, is situated behind the pharynx. The penis and atrium 

 may be considered as a replica, in miniature, of the pharynx 

 and its sheath. 



If the above structures cannot be satisfactorily seen, try 

 preserved, stained, and mounted specimens. 1 



Draw the male reproductive system. Refer to charts and 

 textbooks for anything that is obscure. 



1 Specimens may be readily killed by compressing under a slip, 

 being careful to draw the excess of fluid out on one side so that the 

 animal cannot contract, and running in killing fluid. (Sublimate acetic 

 is good.) As soon as they become opaque white, put on enough killing 

 fluid to float the slip off and transfer the specimens to a dish of the 

 fixative for five minutes, then 50 per cent alcohol a few minutes, 70 

 per cent several hours, stain with borax carmine or Delafield's hemat- 

 oxylin; dehydrate, clear and mount in balsam. (See directions in the 

 appendix for making permanent preparations.) 



