Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . branchiate and tubicolar Anellides, manyof these are dioecious. The sperm-sacs or testes are situated on theventral aspect, between the layers of the ventral muscles. The deve-lopment of the ova is more clear and obvious; because they are com-monly remarkable for the bright colour of their vitelline mass ; andthe number of ova is so great, that the ordinary colour of the anellidis changed at the breeding season. Thus, in the Aphrodite cirrata,Sars found that, in Februar
Lectures on the comparative anatomy and physiology of the invertebrate animals : delivered at the Royal College of Surgeons . branchiate and tubicolar Anellides, manyof these are dioecious. The sperm-sacs or testes are situated on theventral aspect, between the layers of the ventral muscles. The deve-lopment of the ova is more clear and obvious; because they are com-monly remarkable for the bright colour of their vitelline mass ; andthe number of ova is so great, that the ordinary colour of the anellidis changed at the breeding season. Thus, in the Aphrodite cirrata,Sars found that, in February, the three posterior fourths of the bodywere of a brilliant red colour, on account of the great number of ovathere accumulated. Neither testes nor ovaria have external ducts ;the products of both are discharged by dehiscence, into the abdomi-nal cavity, and are excluded by pores situated near the base of thesetigerous feet. In the Aphrodite, the ova pass between the dorsalscales, and there development takes place. There is but one knowngenus of anellid that exhibits external sexual characters, viz., the ANNULATA. :. Sperm-celis and spermatozoa, Lumbricus. Exogone or Cijstonereis. In the females the middle segments exhibitpyrifbrm sacs, attached to their ventral surface, which receive theova after they are impregnated ; the male is without these and issmaller. The genus Eunice is viviparous, and the young escape fromthe ruptured skin of the hinder segments. Finally there remains to be considered the development of the ge-nerative products. As tothe spermatozoa, these areformed in a number of cellsconnected together by aspherical mass, and stud-ding its surface. {^^A.) Each ceU is the seatof development of a sepa-rate spermatozoon, and thisin its growth pushes thecell-wall outward: the fila-mentary extremities di-verge from the commonbasis of the sperm-cells(c) ; then, by mutual attraction, they become amassed together (d) ;and the bundle is finally resolved into the in
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1850
