82 NOTES AND COMMENTS [AUGUST 
A Rare Rotifer. 
In October 1859 Professor Semper discovered in some ditches inter- 
secting rice-fields in the Philippine Islands a remarkable spherical 
rotifer, which he named Zvochosphaera aequatorialis, in allusion to the 
ciliary wreath which divides it into two hemispheres. For thirty years 
nothing more was seen of the creature, until Surgeon Gunson Thorpe found 
it (1889) in Fern Island pond of the Botanical Gardens at Brisbane. 
In 1892 he discovered in some irrigation creeks and ponds near 
Wuhu on the Yanetsze Kiang a new species (JZ. solstitialis) in which 
the ciliary wreath encircles the body as the Tropic of Cancer does the 
earth. In 1896 the same species was found in the Illinois River by 
Dr. C. A. Kofoid, and in 1898 by Mr. H. 8. Jennings, in a pond close 
to Lake Erie. We have taken this information from a short note by 
Mr. C. F. Rousselet (Journ. Quekett Micr. Club, vii. (1899) pp. 190-193, 
1 fig.) who recently exhibited to the Quekett Club a slide of 7. solsti- 
tialis, prepared according to his method by Mr. Jennings. This was 
the first time the animal had been seen in the flesh in England. “The 
anatomy is extremely simple and beautifully displayed, all the organs, 
usually so indistinct and closely packed together in rotifers, being here 
spread out and suspended in the transparent sphere in the most delight- 
ful manner.” It is said that Dr. Kofoid is preparing a full account 
of this remarkable type. 
Does the Organism Repeat Itself ? 
IN an interesting paper entitled “Localised Stages in Development in 
Plants and Animals ” (Mem. Boston Soc. Nat. Hist. v. (1899) pp. 89-153, 
10 pls.), Mr. Robert Tracey Jackson elaborates an interpretation which 
is in direct line with the ideas expressed by Hyatt, Cope, Ryder, 
Beecher, and some other American workers. It is especially in harmony 
with Hyatt’s law of senile characters :—“In the old age, stages are 
found which are similar to stages found in the young, and are prophetic 
of types to be found in degradational series of the group to which the 
animal belongs.” But Mr. Jackson’s particular point is that in addition 
to stages in the young and in the old age, stages may be found in 
localised parts throughout the life of the organism. 
“Tn organisms that grow by a serial repetition of parts, it is found 
that there is often an ontogenesis of such parts which is more or less 
closely parallel to the ontogenesis of the organism as a whole. In the 
ontogeny of such localised parts in a mature individual we find stages 
in development during the growth of the said parts which repeat the 
characters seen in a similar part in the young individual.” 
Such localised stages have been observed in the leaves of plants, in 
branches or suckers of plants, in the budding of some of the lower 
