498 Construction of Maps 



course and termination could not be traced with any degree of 

 accuracy. Half way between the mouth and the first circular 

 spot, there is an opaque irregular mark, which gives origin to 

 the ovary, and which can be easily seen attached to a vesicle 

 in this spot, by its thread-like twisted pedicle. I have never 

 seen more than one of these in the same body, and I have 

 seen it extruded through an aperture at the side of, or near 

 the mouth, as is shown in two of the individuals figured. 

 The ovaries are oval or pear-shaped, and are filled with a 

 granular matter : they are attached in clusters to the body 

 of the Caligus by their pedicles, and may usually be found 

 in great numbers. 



Udonella may be distinguished by the following character: — 

 Body indistinctly annular ; anterior extremity without a 

 sucker ; mouth inferior, longitudinal, edentulous ; eyes none ; 

 posterior sucker plain. — The only known species appears to 

 ba plentiful in our seas; for, of numerous specimens of the 

 Caligus which were brought to me in April, scarcely one was 

 without a crowd of these parasites. 



Art. V. Observations on the Construction of Maps in Geographical 

 Botany. By Richard Brinsley Hinds, Esq. R.N. 



As the subject of geographical botany has as yet met with 

 but little attention, it is not to be expected that any maps with 

 which we may be furnished would convey much information. 

 The few that exist are, therefore, very bare of facts, containing 

 merely the names of some plants, according to their common 

 denominations; without any detail of physical agents, limits 

 of the extension of genera or species, or any circumstances 

 desired by the naturalist. They seem framed more to meet 

 and please the general reader, than for any benefit for the 

 advancement of science. Having lately paid some attention 

 to the subject, a few circumstances have occurred to me, which 

 I think worthy of notice in the construction of these interesting 

 plans. 



It will be necessary, at starting, to make such a division of 

 the surface of the globe as we may deem most consonant 

 with the distribution of vegetation. In the present state of 

 our knowledge of the subject, I am inclined to think that the 

 best that can be adopted is the six-fold one in use in geo- 

 graphy ; namely, into Europe, Asia, Africa, North America, 

 South America, and Australasia. Let us now take any one 

 of these, and, giving a little attention to its general vegetation, 



