PROGRESS OF MICROSCOPICAL SCIENCE. 
249 
of corpuscles as to their number, are very evident from one day to 
another, and this is one of the most striking characteristics of the 
blood of infants. The modifications in the proportion of the cor- 
puscles of different diameters bring on corresponding fluctuations in 
the colouring power of the blood. 10. It is therefore seen that the 
blood of the new-born child shows characteristics specially belonging 
to it, and sufficiently important to allow it the designation of fcetal 
blood. 
Vertebrates Developed without any previous Fecundation.— This is 
asserted to have occurred among some pickerel in possession of 
W. E. L. Sturtevant, who has written the following letter, dated July 
8th, to the Smithsonian Institution, U.S.A. He says that “on March 
5th, 1875, the boys brought in some brook pickerel. One was swollen 
with spawn, weight of fish 521 grains ; of spawn freed from membrane, 
127 grains, 117 spawn weighed 5 grains. Therefore whole number 
about 2972. This spawn was amber coloured, and the eggs were in 
general translucent Occasionally an egg could be seen which was 
slightly smaller than the rest, and clouded, and some few were opaque. 
These eggs, thus marked, presented different appearances under the 
microscope. I have mislaid the notes and drawings that I took at 
the time, but can furnish the following facts from memory. The 
clouded eggs showed a different development from the others, there 
being a greater difference in size of the cells, and occasionally the 
cells arranged in lines. Some of the opaque eggs had evidently 
developed in the line of the fecundated egg, as the cells were arranged 
in the form of a curled fish, the line of the back being well defined, 
the line of the belly and sac poorly or not at all defined, while there 
was a concentration of cells about the locality of the eye. I cannot 
say that I saw a young fish, for I did not. but I saw what I considered 
sufficient to interpret as development to a certain degree, without 
fecundation. I was so much surprised, that for a time I doubted my 
own eyesight, and called my brother to look. He saw what he called 
a young fish in the egg, and so I was convinced, but I had not the 
courage to send my observations to men of science. This next spring 
I will try and procure some fresh specimens, and if my observations 
can be verified, as I doubt not but that they can be, I will send them 
to you.” 
The Ascidian Oritjin of Vertebrates. — This subject has, of course, 
been referred to in the address of the President to the British 
Association. Dr. Thomson said, in referring to the notochord that it 
is a continuous median column or thread of cellular structure, running 
nearly the whole length of the rudimentary body of the embryo, and 
lying immediately below the cerebro-spinal canal. It occupies in 
fact the centre of the future bodies of the vertebra. It exists as a 
primordial structure in the embryo of all vertebrates, including man 
himself, and extending down to the amphioxus, and, according to the 
remarkable discovery of Kowalevsky in 1866, it is to be found among 
the invertebrates in the larva of the ascidia.* In amphioxus and the 
* ‘ Mem. de l’Acad. de St. Petersbourg,’ vol. x. 
