J322 Dr Gairdner's Analysis of 



also passes through the same phases of a transverse division 

 into two equal independent animals. The third method is the 

 true gemmiform division, as in the Hydrae and Planariae, in 

 which a small bud is given off from the posterior surface of the 

 animal, which is provided with ciliae, and when separated from 

 the parent trunk, is still of a very diminutive size. 



Such are a few of the observations on the generation of these 

 animals, from which it will be seen that they are but in their 

 commencement, and that much remains to the patience and la- 

 bour of future observers. 



4. Vascular System ? — The existence of a digestive, a mus- 

 cular, and a generative system of much complexity, and very 

 far from what we might consider as their simplest expression, 

 may now be viewed as an ascertained fact with regard to infu- 

 sory animals. The existence of the two systems which remain 

 for our attention, viz. the vascular and nervous, is as yet some- 

 what problematical. The organs on which Dr Ehrenberg con- 

 fers these appellations, are very apparent, but much doubt ex- 

 ists with regard to their real functions. 



What has been denominated a vascular system is distinctly 

 visible only in the Hydatina serda. Traces of a similar arrange- 

 ment are now and then perceptible in the Eosphora, in particu- 

 lar positions of the animal, but they quite disappear when the 

 integuments are in a state of strong tension. In the former, a 

 series of transverse lines of a white colour, and inferior transpa- 

 rency to the rest of its body, succeed one another at regular in- 

 tervals, from the head towards the tail. These transverse striae 

 might at first be taken for muscles, but they differ from these 

 entirely in their aspect and connections. They are nine in num- 

 ber exactly parallel to, and nearly at equal distances from, each 

 other. At first sight they seem to be complete rings encircling 

 the whole body ; but, upon a closer inspection, they are ob- 

 served to diminish in breadth, and finally vanish on approach, 

 ing the inferior or abdominal surface of the animal. On the 

 contrary, they augment in diameter towards the back, where 

 they all terminate at right angles, in a line, of an exactly similar 

 appearance to themselves, running in a longitudinal direction 

 from the head to the tail. This longitudinal line or vessel is 



