306 PHILLIPS—-A REVIEW OF PARTHENOGENESIS.  [0ct. 16, 
head composed of bones arranged in a cube and surmounted by 
three teeth. The bones of the feet and hands were perfectly rec- 
ognizable. There was no alimentary canal in the body, but beside 
it was a tube which histologically resembled an intestine. 
It would appear then that these phenomena are not true partheno- 
genesis, unless it be that we consider that as the explanation of the 
cysts. The fact that the cleavages do not follow the regular plan 
of fertilized eggs would not of itself bar these cases as being classed 
as a true development from an unfertilized egg, since in other cases, 
where there is undoubtedly a parthenogenetic development, the 
method of growth differs from that of the fertilized egg of the same 
species, ¢.g., Leptodora. Neither must we bar these cases because 
the development goes but a short distance, since the life of an 
individual must be considered as beginning with the unsegmented 
egg, and if that egg shows a power of development without ferti- 
lization, that phenomenon is as truly parthenogenesis as if an 
adult animal resulted. However, since in these casés we find the 
segmentation of the egg to be more in the nature of a physico- 
chemical change than a true cleavage, we must consider it as 
entirely different, and we must, of course, bar out all cases in 
which the proper amount of care has not been taken in proving 
that fertilization has not been aftected bya half-dead spermatozoon. 
ARACHNIDS. 
But one well authenticated case is known to exist in Spiders 
(Campbell, 1883). Parthenogenesis in this group has recently 
been discussed by Montgomery (1903), and it is not necessary to 
repeat his discussion since it has been done so recently. 
In many other animals there is a marked tendency for the mature 
egg to go on dividing if fertilization does not take place. This is 
often observed in Echinoderms, some Annelids and Molluscs. Such 
eggs never develop beyond a very early stage, and only a very 
small proportion of eggs show this cleavage. A point worthy of 
note is that these very forms are the ones which have yielded the 
best results in work done in Artificial Parthenogenesis, and the 
explanation which seems to follow from this is that such eggs 
normally require a very small amount of stimulus from the male 
cell, and the addition of some chemical to the water is enough to 
take the place of the male stimulus. In fact the results of artificial 
