THE INVERTEBRATE COURSE. Ill 



without being too hard for satisfactory dissection. One and a 

 half days should be spent on this dissection, although the fa- 

 miliar device of allowing half the class to work out and demon- 

 strate the circulatory system while the others reciprocate with 

 the nervous system, disposes of the dissection in a day. 



Cephalopod study is limited to the common squid, Loligo. 

 Living specimens are in the students' aquaria and in the central 

 tanks through the week ; egg laying frequently occurs. The most 

 spectacular demonstration of the course comes when the living 

 squid are injected through the buccal sinus for venous system and 

 through the heart for arterial, and studied immediately in salt 

 water. Almost the whole system can be made out without cut- 

 ting. The better prepared students make the complete dissec- 

 tion of the spermatophoric organ, for which directions are found 

 in the third additon of Drew's Manual. It is obvious that in this 

 work, as on Busycon, there is not time for finished dissections and 

 drawings, but it is surprising how much good work can be done 

 in the concentrated effort of a long day, especially if drawings of 

 external features be largely omitted. 



Chordata. Two days, lecture and laboratory. Chordate 

 studies are limited to the Hemi- and Urochordata. The work be- 

 gins with a study of external features of Dolichoglossus. These 

 may be collected Saturday afternoon and kept until Monday in 

 good condition if placed in separate bottles over which a good sup- 

 ply of water flows. The remainder of the first day is spent 

 largely on Molgula, living and preserved. 



Pcrophora is used to demonstrate the circultion and the modi- 

 fication found in a stolon type. Young Botrylhts, that are still 

 transparent, are also present in the laboratory in reserve. Ainara- 

 c in in tadpoles, alive and stained, take up the last morning of the 

 course. The last afternoon is spent in working out some form, 

 such as the adult Amaroecium, with no help other than that to be 

 found in texts and laboratory guides. The exercise is not an 

 examination ; it counts no more in our estimation of the ability of 

 students than that done on any other half day. It gives the 

 student an opportunity to orient himself under conditions less 

 favorable to rapid work than those that prevailed in the preceding 



