The mass of the body consists of richly branched stellate cells - the mesenchyma - and imbedded in this plasmic tissue are the nervous, excretory, muscular and generative organs.
This is the mesenchyma.
Some of the central cells remain in clumps as "germ-balls," others form a mesenchyma in which "flame-cells" arise; others again give rise to muscles; and at the thicker end of the body, rudiments of the brain and digestive system are observable.
In addition, some show duplication of the gonads and of their ducts, so that we find both transverse and longitudinal repetition of these organs, without corresponding multiplication of the nervous ganglia mesenchyma, or excretory opening.
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