File:...The Apodida, a morphological study (1892) (14587390588).jpg

Identifier: theapodidamorpho00bern (find matches)
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Year: 1892 (1890s)
Authors: Bernard, Henry Meyners
Subjects: Zapodidae
Publisher: London, New York, Macmillan and co.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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IMG. 40.—Second larval stage of Lepidurus productns (after Brauer). Crustacea a comparatively small, and for each groupa fixed, number of segments. Between these two theApodidae form the true link, having a diminishingnumber of segments, diminishing, that is, by a con-siderable number remaining undeveloped, and sorudimentary as to be useless to the animal, and there-fore liable to vanish. In this section on the Nauplius we have appealedto the developmental history of A pus in support of 168 THE APODID^E PART 1 the arguments founded upon anatomical and morpho-logical comparisons brought forward in the previoussections. \Ye may, we triink, safely maintain that the
Text Appearing After Image:
FIG. 41.—Fourth larval stage of Apus (Glaus), the diverticula of the mid-gut com-mencing to form the glandular imaginations (/). bulk of the evidence to be deduced from the Naupliusis decidedlv in favour of our theory. To us it seems ^ »* so strong, that on it alone the theory might almost be SECT, xi DEVELOPMENT 169 based. All that our argument requires is, that, whilethe positive evidence is strong, the difficulties shouldnot be insuperable. \Yc have had to limit our remarks to the larvalhistory of Apus, as observations on its embryologicaldevelopment arc unfortunately wanting. We ma),however, here mention one or two facts in the embry-ology of the Crustacea which bear upon our theory. Itis stated,1 for instance, that the median eye developsfrom paired rudiments—an observation which lendssome support to our account of the origin of thisorgan out of an anterior pair of eyes. Still moreimportant for our theory is the fact that, while in thedevelopment of a few Crustacea there is

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