THE AMERICAN NATURALIST [Vol. XLII 



lism in the two sexes. If its cause is a substance in the blood 

 it may be "inherited" from the female alone, and the male 

 which manifests the disease can not transmit it. Thus it would 

 be a case of transmission through somatic elements rather than 

 through the germ cells. 



F. T. L. 



INVERTEBRATE MORPHOLOGY 

 Form Variation in Amblystoma tigrinum — Powers 1 has observed 

 the aquatic forms of this salamander both in their natural en- 

 vironment and under artificial conditions. His paper contains 

 a large amount of material of great interest which would be 

 much clearer reading if the numerous observations and experi- 

 ments had been more explicitly described as to objective point 

 and methods employed. The paper is too long for condensation 

 here, but a few of the results can be noticed and will be welcome 

 to those interested in the axolotl question. He distinguishes 

 two main types, the ordinary larvae and the cannibals, both by 

 habits and in important points of structure. Taking the ordi- 

 nary form first, two types as a body form are recognizable : those 

 with the habit of crawling about on the bottom in a sluggish 

 manner and thus living largely in the dark, these are of a 

 broader shorter form and arc called the "robust type," and a 

 second type of quite different habit, being active swimmers going 

 about actively in search of their prey, and of an elongate slender 

 form, the "slender type." There is a great difference in the 

 ratio of head width to total length in these two types, head 

 width being contained 6.42 in total length in the robust type 

 and 11 times in the slender ones. The mode of feeding is quite 

 different in these two types. In the robust bottom-living forms 

 food is obtained by using the mouth as a sieve and opening 

 it widely to strain water through it in hopes of finding food 

 thereby, with the result that the gape is increased. On the other 

 hand, the slender swimming forms go about actively in search 

 of prey, which, when they see it, they actively seize so that the 

 mouth is not opened so widely as in the sieving process of the 

 sluggish robust type. He also notes variations in special parts, 

 such as the tail, the head and the posterior limb. Tails vary 

 1 Powers, J. H., '07. Morphological Variations and its causes in Am- 

 blystoma tigrinum. Studies from the Zoological Laboratory of the Uni- 

 versity of Nebraska, 71, pp. 1-77, pis. i-ix. 



