270 ORDER FLAGELLATA.PANTOSTOMATA. 



with that of some highly finished machine, into one end of which the raw and 

 heterogeneous material is flung to issue at the opposite extremity a perfected and 

 homogeneous fabric. On first passing away from the monad's body this stem is 

 perfectly soft and glutinous, it gradually hardening and acquiring its dark brown 

 hue with exposure to the water. It is only after this prolonged exposure, more- 

 over, that the longitudinal striae previously described make their appearance, 

 such striae again obviously representing the outlines of the individual contributions 

 of each separate monad towards the common fabric, and these separate elements 

 become fused with one another during their pristine soft and plastic state. The 

 ordinary method of increase of the monad clusters of this species, namely by 

 rapid longitudinal fission of the individual zooids, assists materially in demon- 

 strating the opinion here expressed, as to the significance of the striae, for as the 

 stem grows longer and the monads continue to multiply in number the longitudinal 

 striae become also correspondingly more numerous. That there is a permanent 

 hollow core in this structure, as has been maintained by James-Clark, is certainly 

 not supported by the results of the author's investigations. That new-formed 

 part of the stem near its point of junction with the terminal monad group, no 

 doubt exhibits a firmer consistence exteriorly where it comes into direct contact 

 with the water, but this distinction is only temporary and becomes entirely obliterated 

 as the stem increases in age and strength. 



Multiplication by longitudinal fission, as already indicated, represents an ordinary 

 method of increase in these animalcules ; a primary single monad dividing inde- 

 finitely, after the manner of Codosiga or Epistylis, until from the single individual 

 which laid the foundation of the colony, one or more mulberry-like clusters are 

 formed numbering respectively some fifty or sixty individual zooids. Now and then, 

 these terminal clusters break away, and forming new attachments develop compound 

 clusters similar to those from whence they originally sprang. Doubtless, however, 

 there is another more complex method of increase manifested by this species, 

 analogous to what has been already observed of numerous other Flagellata, 

 obtained through the genetic union of two or more individual zooids, and followed 

 by the production of innumerable independent germs or spores. Although up to 

 the present time no direct evidence of such a sporular mode of reproduction is 

 forthcoming, the following phenomena, observed by the author, may possibly serve 

 as a clue towards the supply of this, as yet, missing link in the life-history of the 

 species. 



In the month of August 1871, the examination of a leaf of Myriophyllum led 

 to the detection of an oval body adhering to it, closely resembling the egg of some 

 free-swimming Rodferae, as represented at PL XVII. Fig. 20. Movements being 

 in progress within this body, promising the early release of its contents, attention 

 was specially concentrated upon it. Only a short interval had elapsed, however, 

 before it became evident that the transparent shell contained innumerable independent 

 organic particles in place of the single multicellular germ of an ordinary Qgg. As time 

 progressed these separate particles began to exhibit violent ebullition-like move- 

 ments as though endeavouring to break through the prison wall that encircled them. 

 At the end of half an hour a rift suddenly appeared at one extremity, and a second 

 inner investing membrane was protruded funnel-wise through the aperture, as shown 

 at Fig. 21. The energetic or, so to say, excited motions of the imprisoned particles 

 became now greatly augmented, till at length bursting in its turn (Fig. 22), this 

 second inner capsule let loose into the surrounding water a countless swarm of 

 minute, reniform, uniflagellate animalcules. These monadiform germs, which pre- 

 sented a remarkable resemblance to the somewhat similarly developed progeny of 

 Physomonas socialis, and also to the adult form of the Pleuro7nonas jaculaiis of Perty, 

 enjoyed their free roving condition for but a brief interval. Within a few minutes 

 after their escape they became sluggish in their movements, and settling down on 

 the surface of the glass slide withdrew their flagella and changed their shaj)e from 

 reniform to spherical, as shown at Fig. 25. In this quiescent state these spheroidal, 

 and apparently encysted, bodies remained for the next twelve hours, when an accident 

 occurred which interrupted the further investigation of dieir life-history in so 



