THE INVERTEBRATE COURSE. 109 



This laboratory work has sometimes been introduced by a study 

 of the 48-hour Hydroidcs trochophores. The primitive structures 

 can be easily made out. These are followed by 5-7 day larvae 

 showing the greater development of the tail region. 



Bryosoa. One day, lecture and laboratory. Living Bugula 

 furnishes the main attraction, and some time is spent on the en- 

 crusting forms. 



Crustacea. Three days, lecture and laboratory. The treatment 

 of this phylum has undergone more changes than that of any 

 other group in my eight years on the course. At one time a week 

 was spent in detailed study of their homologies. 



\Ye give one afternoon of the three days now allotted them to 

 studying tow, which contains a large number of larval crustacean 

 stages at this season of the year, but is examined for other animals 

 as well. 



The lobster is the introductory animal, with the blue crab as 

 alternate for those who have already dissected the lobster or the 

 crayfish carefully. These are injected and hardened (see ap- 

 pendix IV.) in formalin for two weeks before using. One day is 

 given to this dissection, with a'n extension of time for those who 

 need it. More time could well be spent here but it is better used 

 elsewhere in this crowded course. Some study is made of the 

 usual Entomostraca, such as Cyclops and Argulns and a half day 

 is spent in working out appendages of Malacostracan forms, 

 which are recorded as shown in appendix V. While on the chart 

 rack the information given in appendix VI. is displayed to aid the 

 students in making comparisons readily among the forms studied. 



The work is finished by a half day spent in dissecting Lepas 

 with Balanus present for comparisons. Among the interesting 

 side lights that have been presented from time to time the follow- 

 ing have been especially successful : 



Argulns placed in finger bowls with Fund id us attach them- 

 selves to the fish and change color as the Fundulus change from 

 being placed on different backgrounds. This is difficult because 

 of the time required to accumulate enough Argulns. 



Blood coagulation is shown in Oniscus by snipping off the fila- 

 mentous tip of the antennae. A drop of blood is caught on the 



