136 



stron<>er than 7U percent, it will not canst' this swflliny of the nieniltrano. Altrr 

 tliis the eggs can be dealt with alter tlu' rcuular methods. 



To stndy the segmentation the eggs may !)e kept in a watch-ghiss, and ex- 

 amined with a strong lens or low power of the microscope. The formation of the 

 fnrrows can he studied up to the 32-eelled stage with practic.illy no diflicnlty, and 

 with some cari' to the 12S-cel1ed stage. Eggs at the various stages n'lay be killed, 

 hardened and sectii)ned so as to show the internal changes, the formation of the 

 cleavage cavity, the archenteron, notochord and other organs that appear from 

 tinu' to x'unv. In the process of clearing the eggs it is bc'st to n>e cedar idl 

 rather than tnri>entine, for the latter tt'nds to make them even more brittle 

 than they are. 



The general progress of tiiis development is too wtdl (lescril)ed in text-books 

 to merit anv further account here. I am indel)ted to I'rof. Th. 11. Morgan, of 

 Rrvn Mawr college, for most of the above points. I have carefnily tested them, 

 and can recommend them without restricting (inalilications. 



Another interesting field in the stndy of these eggs is to sep.-irate the seg- 

 ments in the earlv stages of segmentation and observe the result. It has been 

 found that in the two-celled stage each segment will form a |)erfect animal, 

 but onlv about half the normal size. This has been tested as far as the eight- 

 (•(dled stage, each segment c-ontinuing its developnu-nt, Ixit forming s|)ecimens 

 much smaller than ordiiuirily, the effects of pressuie up<»n the developing eggs 

 causin" them to segment in a difl'crent manner. < >ther points of interest miglit 

 be suggested, but these are sutiicient to call attention to this important snbje<-t. 



PoisoN'Ofs lNi'i.rKN(E OF Vakious SfEfiKs OF ( 'v I'Ri fi:i>iuM. I'.y 1 >. T. Mac- 

 Do rG.\L. 



At the last December meeting of the Academy a short paper was presented 

 bv the writer detailing souu' observati(nis tending to show that C. sprctabi/e and 

 C piibesrens have an irritant action on the human skin. This jiaper was printed 

 in full in the "Minnesota Botanical Studies," Part 1, li'J, 1S94. 



The interest in the matter shown by the commt'nt of the scientilic and daily 

 press and by the large am(Uint of correspoiuleiu-e received, was such that a series 

 of tests were planned which would place the entire matter beyond all (piestion or 



doubt. 



It had been suggested by ingenious correspondents that the poisonous effects 

 experiencetl by the writer in handling C. specfabile in a swampy location, may 

 have been due to the action of some of the poisonous plants, such as Rhn.^. usually 



