The Morphology of Cosmobia 3G1 



ogists), leads to the conclusion that both sorts of monsters are clue to 

 the same cause or kind of cause, and that they should be considered 

 together in any general treatment of the subject, especially in all dis- 

 cussions concerning the cause of these monsters. It seems, further- 

 more, that all members of this series, both normal and almormal, are 

 equally subject to definite and orderly laws of development, the impulse 

 to the formation of which lies, in the one case as in the other, within 

 the organism, and leads in all cases to the formation of beings which 

 are primarily symmetrical and free from all pathological tissue or any- 

 thing which is out of harmony with the organism as a whole. It must 

 be remembered, however, that the word "primarily" is always to be 

 understood in connection with the above statement, for even in the case 

 of perfectly normal germs, later causes, mainly external, may lead to 

 very great deformities, through which the resulting organism is led to 

 deviate from the original goal. Since this is often so in individuals 

 primarily normal, where all the conditions of development have become 

 long adapted to an embryo of a certain definite form and size, how 

 much more likely to become secondarily deformed must be an organism 

 unusua] and unwonted in these particulars? If we consider the perfect 

 adaptation of the uterus, the placenta, the yolk-sac, the egg-shell, and 

 the other adjuncts to development that appear in the different classes 

 of vertebrates, we wonder that any embryo of abnormal shape can ever 

 attain an advanced stage without secondary deformations rather than 

 that some of them should become thus. It seems also very probable 

 that monsters vary in their susceptibility to secondary deformation, 

 and that, while certain types usually come to maturity and are even 

 viable, others may inevitably encounter some adverse mechanical principle 

 at an early embryonic stage. Thus the deformed proboscis that repre- 

 sents a nose in several of the types of the series in question, probably 

 develops without deformation up to the time at which the descent of 

 the fronto-nasal process should begin, and the deformity that then begins 

 to make its appearance, although an inevitable one, is due to no deficiency 

 in the germ, but to an unfortunate mechanical relationship which 

 appears at this time Should an embryo of such a monster ever be 

 obtained at a time before the fronto-nasal process begins its downward 

 growth it is safe to predict that there will be nothing in this region 

 which may be considered a deformity, but that the parts will be svm- 

 metrically and orderly arranged as in the case of those parts which are 

 not hindered during development. 



