Hy:itt.] 106 rApril 5, 
soein to liavf Ixhmi laroely derived from the inimediate ancestors 
of the species. Thev often have their corresponding ph yletic forms 
witliin their own family or genus, whereas the cliaracteristics of 
tlie ananepionic substage are derived from remote ancestors. 
Thus by the aid of direct observation it is not difficult to see, 
that the substages of development in ontogeny are the bearers' of 
distal ancestral characters in inverse 2'>'>'oportion and of proximal 
ancestral characters in direct proportion to their removal in time 
and position from the protoconch or last embryonic substage. . It 
is already generally admitted that this law is true of the embryonic 
stages themselves with reference to the protembryo, although 
most observers would hardly dare state this in the same positive 
terms as here employed because they are confused by what they 
call abbreviated development. They have not traced the system- 
atic regularity with which the law of tachygenesis works in pro- 
ducing the replacement of hereditary characters in every series 
of forms, and do not trust or know how to use this law. 
That this law of development is also paralleled in the evolution 
of the jjhylum, so that the stages of evolution exhibit the distal 
ancestral characteristics in, inverse jyroportion to their removal in 
time and in adult structure from their point of origin^ is a law I 
have tried to demonstrate in several publications and have only to 
add that recently gathered evidence is making this position still 
stronger. 
The transformations that distinguish the subdivisions of the 
neanic stage are very well marked in some forms and less 
distinctly in others, but I have continually found the need of defin- 
ing two stages. Ananeanic is a suitable term for the first sub- 
stage, which is usually well marked in nautilian^ shells by the first 
appearance of the impressed zone. This is the name I have given 
to the area on the dorsuni affected by the contact of the dorsum 
of the growing whorl with the venter of the already formed 
whorl of the next inner volution. This is either flat, gibbous, or 
indented in accordance Avith the form of the venter of the whorl 
it touches or envelopes, but it is usually indented more or less 
deejdy. 
1 In my Genera of fossil cephalopods nautilian forms have been defined as those 
havinj; the whorls in such close contact that the dorsum of the enveloping or later 
formed whorl is modified, either flattened or bent inwardly along the area of contact, 
and has what is called an "impressed zone." 
J 
