File:Contributions (1898) (20063716374).jpg

Title: Contributions
Identifier: contributions06brow (find matches)
Year: 1898 (1890s)
Authors: Brown University. Biological Laboratory
Subjects: Biology
Publisher: Providence, R. I
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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204 Journal of Comparative Neurology and Psychology. moulting, but never between moults. From the fourth stage on, each successive stage-period is of longer duration and the changes which the adolescent lobster thenceforth undergoes are corre- spondingly less significant, being characterized chiefly by altera- tions in internal morphology as the adult functional type is grad- uallv approximated. The first three stages of the lobster are free-swimming stages, and the activities are without apparent
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Fig. I. Showing a young first-stage larval lobster about two days old. The eyes are large and promi- nent. The exopodites of the thoracic appendages are represented at the beginning of the downward stroke. This figure shows the typical swimming position of lar\-ae in the first three stages, the plane of the cephalo-thorax bent down at an angle of about 30° from horizontal. coordination or aim. The larvae are swept here and there by the tide and possess no power to evade the attacks of numerous enemies. The swimming of the lobsters of the first three stages is accom- plished by means of the feathered exopodites, or outer branches of the thoracic appendages (Fig. i). These exopodites beat the water with short vibratory strokes, which tend to carry the larva back-

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