144 Report of the Microscopical Section. [Sess. 



the following names are now more generally used — hyaloplasm 

 for the former and spongioplasm for the latter. 



Owing to the gelatinous substance of the amoeba, its form 

 is continually changing. It protrudes part of its substance 

 like a foot, and thus moves itself along. The parts thus pro- 

 truded are called pseudopodia. The amoebae feed upon minute 

 algae and reproduce themselves by fission. 



Leech. — The next type was the Leech {Hirudo medicinalis). 

 Dissection in invertebrates should be commenced from the 

 dorsal side, while in vertebrates it should be commenced from 

 the ventral side. As a rule, all such dissections should be 

 done under water. 



The external characters of the medicinal leech are — body 

 with numerous rings ; on the dorsal side a line of a brownish 

 colour on each side of the median line ; general colour olive- 

 green. At the posterior end there is a large sucker which 

 serves for the purposes of attachment, and at the anterior end 

 a smaller sucker in the centre of which is the mouth. The 

 biting apparatus in the mouth consists of three semicircular 

 toothed plates. 



Internal Orgcmisation. — The alimentary canal extending the 

 whole length of the body is provided with eleven dilatations 

 or lateral pouches on each side. The gullet is very short, and 

 the intestine slender. The male and female organs are in the 

 same individual, but the leech is not self-impregnating. 



The Earthworm {Lumhrictis terrestris) was the next type 

 studied. The dorsal side of the animal is of a purplish colour, 

 while the ventral side is whitish. The body is divided into a 

 number of constrictions or segments called somites, which cor- 

 respond to internal divisions by septa. The mouth perforates 

 the first segment, which is subdivided into a dovsal prostomium 

 which overhangs the mouth ; and a circumoral peristomncm. 



In sexually mature specimens there is a whitish saddle- 

 shaped enlargement on the dorsal side called the clitellum, 

 which is connected with the act of reproduction. The dark 

 line on the dorsal side is the large dorsal blood-vessel. 



The locomotor organs consist of four double rows (two ventral 

 and two lateral) of bristle-like appendages called setce, of a 

 curved needle-shaped form. 



The alimentary system is a straight tube running the 



