The Microscope. 231 



Fig. 10-14. — Final division of tlie pollen-spores of the wild-onion {alium 

 CaTiadense. In Fig. 10 the nuclear-plate is shown. In the cell at 

 the right it is seen in profile, in that on the left from above. 



THE HISTOLOGY OF LUMBRICUS, OR THE EARTH- 

 WORM.-!. 



HENRY L. OSBORN, PH. D., 



PROFESSOR OF BIOLOGY, HAMLINE UNIVERSITY. 



PLATE IV. 



THE earthworm by reason of its easy capture, its zoological 

 position, its convenient size and its soft boneless structure, 

 has fallen a prey to hundreds of biologists. A large number of 

 excellent researches treating of its histology are now published, 

 but though the subject has not even yet been exhausted, a most 

 active controversy being waged in the current journals upon 

 certain points in the embryology, itis not the present intention 

 to undertake to add any to our knowledge of earthworm histo- 

 logy. The purpose at this time is merely to set forth for the 

 benefit of students the methods of histological study ; using this 

 very convenient creature as the subject. 



Specimens of Lumbricus having been obtained, they must first 

 be subjected to an anatomical examination before any histologi- 

 cal study is made, since the interpretation of , the histological 

 structure is unintelligible except as the sequel of at least a rough 

 dissection. To prepare the specimen for this study, immerse it 

 in water and add alcohol in small amounts so as to stupefy the 

 creature gradually. When it has becom.e inert and apparently 

 dead, draw off most of the water and add alcohol so as to in- 

 crease the strength to 30-50, finally 95 per cent. Leave the 

 specimen to harden in 95 per cent, alcohol at least 24 hours. 

 Directions for dissection can be found in any of the numerous 

 guides for the use of students*. 



The anatomical study will demonstrate the dorsal and ventral 

 surfaces, the ringed body, the 8 rows of setse, the body cavity, 

 the large pharynx, the dorsal brain, the nerve collar and the 

 ventral cord, segmental organs in the anterior portion of the 



* The book of instruction most satisfactory for the purpase of the general student 

 of this subject is General Biology by Sedgwick and Wilson. For the dissection of the 

 Lumbricu* sufficient directions are given in the Invertebrate Dissections of the writer. 



