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Show 150 DR. W. B. BENHAM ON [Feb. 16, presented by the position and arrangement of the internal organs, which I have just mentioned, in Kynotus, and, still further, the position of the few genital organs described by Michaelsen, I am inclined to put a different interpretation on his " segments," and hence a different enumeration of " somites." In K. madagascariensis the only genital organs observed are the spermathecce ; these are in a condition similar to that of Microchceta ; they are in rows of 22, 26, and 25 small sacs along the anterior margins of the "segments" 23, 24, and 25 respectively; the rows extending nearly all round the body. In K. longus there are four rows of eight spermathecae-one row on each side of the anterior margin of the "segments" 25 and 26. In this species he observed the sperm-sacs, of which there appears to be a pair in front of each of the septa vi. and vii. [" Ein Paar umfangreicher Sacke, vor den Dissepimenten vi. und vii., deutete ich als Samensiicke " ]. Now, if it be borne in mind that between the septa v. and vi. there are, according to Michaelsen's mode of reckoning, two " segments," namely the 16th and 17th, and between the septa vi. and vii. likewise two "segments," the 18th and 19th, we get the sperm-sacs occupying a very abnormal condition indeed ; for in what Earthworm, of ah the many genera, do we find the sperm-sacs originating as far backwards as the 16th " somite" 11 They usually occur in any somite from the eighth to the twelfth, and where there are two pairs they nearly always originate in somites x. and xi., or in somites xi. and xii. I believe this apparently abnormally posterior position of the genital organs and the other peculiarities of Kynotus can be explained by interpreting the external rings, not as "segments" but as annuli; then between every two consecutive septa in the anterior part of the body we shall have not two "segments" but two annuli, that is one somite, and we shall find that matters work out more in accordance with what we find in other Earthworms. Granting that the gizzard lies in somite vi., which is a very usual position for the organ in the family Rhinodrilidce (amongst which Michaelsen places the worm), as well as in other families, the first septum lies, not between " segments " 7 and 8, but behind somite vi., the second behind somite vii., and so on ; this brings the sperm-sacs into somites xi. and xii. (where they do occur in Micr. rappi, in Rhinodrilus, Hormogaster, and perhaps in Brachydrilus), and the spermathecae are then in somites xv. and xvi. in K. longus, and in somites xiv., xv., and xvi. in K. madagascariensis; and this position agrees with that of the sacs in Mic. rappi. Again, the nephridia will be one to each somite. Michaelsen remarks on the variation in the position of the pores in the anterior region of the worm, where they lie in some " segments " just behind the septa, in others in the middle of the " segments" ; he sees only one explanation of this, that the nephridia were orisinallv one 1 The condition of the sacs in Geoscolex, Urochceta, and Diachceta is quite different ; they m a y extend into these somites, but originate in a more normal position. |
