202 THE NORTHERN MICROSCOPIST. 
ere Joe ne ee Se 
enter eggs. Yet we know that this latter is true. But something 
may be learned {from the observations of Cienkowski on Vampyrella 
spirogyre, seen in Fig. 14; @ is the mature form engaged in the 
work which distinguishes it, ze, boring into the cells of the 
spirogyra. It then withdraws its pseudopodia, is granular, and 
divides into three portions within a cell, 6. These each escape, 
and become amceboid, as we see at c Each of these again 
becomes at length encysted. Thus we have an amoeba stage, a 
cell stage, a second amceba stage, and a final encysted stage.* 
. This is not a perfectly worked out form, but it has none the less in 
this relation a suggestive history as to its penetration of vegetable 
cells. 
The same caution is necessary in reference to the occasional 
appearance of the accidental “ grouping of chlorophyll grains.” 
Something may be learned from the history of Pediastrum granu- 
latum, the mother cells extruding granules in colourless (and at 
first almost invisible) envelopes, in an irregular manner ; but these 
granules afterwards arrange themselves in their hereditary order, 
and become as their predecessors. But much by way of cautious 
investigation must also be added. Indeed, the lesson throughout 
is caution. Some illustrations, indeed, as many in this Society 
will remember, were given us from that admirable observer, Mr. 
FE Carter, F.RS. These observations, however, which are very 
far from parallel with those adduced in comparison here, were 
made over twenty years ago. But since that time Mr. Carter has 
corrected, by further observations, what he discovered to be 
erroneous in his earlier results, explaining the paradoxes by the 
presence of parasites with whose existence he had not been before 
acquainted. + 
We can only assume that this correction of the facts was 
unknown to the author of the paper which we criticise. Even 
Louis Agassiz, if we are only to allow his earlier work to bear 
witness uncorrected by his later, could be quoted as strongly on 
the side of Heterogenesis, Thirty years ago he asserted that the 
Trichodina was a Medusa! “In the eggs of Hydra he had been 
able to trace all the forms from the segmented yolk to these para- 
sites; the fresh-water Hydra is the polypoid form of Meduse, 
while these parasites are the medusoid form.” Further, he says, 
“I have seen a Planarian lay eggs out of which a Paramecium was 
born (!), which underwent all the changes these animals are known 


* Cienkowski. Leitrige zur Kenntniss der Monaden. Schultze Archiv. Sur 
Microscopische Anatomic, Bad. i1., 1865. 
+ Cf Ann. of Nat. Hist., \and ser., vol. xix., p. 287, and Aun. of Nat. 
f7ist., 3rd ser., vol. Vill., p. 289, 
+ Proc. Boston Soc. of Nat. Hist., vol. lii., 1850, p. 354. 


