RHIZOPODA. 
581 
of the presence or absence of the fibrillary layers. The nucleoli also 
may bo wanting, and the nucleus always disappears shortly after the 
encystation. The species which are provided with an apparatus of 
attachment are only fixed to the intestinal channel of their hosts 
during a certain part of their life ; the “ epimerite,” or the portion 
of this segment forming the adhesive apparatus is thrown off and the 
fixed stage (“ cephalin ”) followed by an errant stage of life (“ spora- 
din”). The encystation may be solitary or combined with a false 
or real conjugation. The dissemination of the spores is ordinarily 
the result of the bursting of the wall of the cyst, but in Clepsi- 
drina and Gamocystis of more complicated structural arrange- 
ments — the sporoducts. Though the shape of the spores (** pseudo- 
navicellae,’* “ psorospermia ” of authors) are ordinarily very regular and 
characteristic of the genera, it may also be very variable (e. g., in 
the Monocystis of the earthworm) ; a distinction may sometimes be 
made between “ macrospores ” and “ microspores.” In Urospora, the 
spore is provided with a rigid tail. In some genera with a “nucleus,” 
in each spore, 6-8 falciform nucleated corpuscles are developed and set 
free through the rupture of the spore (^Gonospora, Urospora^ Dufouria^ 
Monocystis). The transformation of these bodies into an amoeboid 
stage was not observed, but is perhaps probable, from analogy with 
the “ falciform corpuscles ” of the “ oviform psorospermia ” of Mam- 
malia, which cannot, according to Schneider, be separated from the 
Gregarinidce ; but it is also possible that these bodies are directly trans- 
formed in young Gregarines. The Gregarinidce are incontestably animals 
and Protozoa ; they are (when the “ Psorospermia oviformia ” of the 
Mollusca are not taken into account) rare in Ascidice and Holothuridce , 
less rare in Turhellaria, Choetopoda, and Gephyrea, and rather abundant 
in Insecta and Myriopoda, the several order of Insecta differing, how- 
ever, largely in this respect ; they are also relatively rare in A rachnida 
and Crustacea. The Monocystidea are either inhabitants of the alimen- 
tary canal or of the common body-cavity, they are rare in Arthropoda ; 
the Polycystidea, on the other hand, are limited to the intestinal tube of 
this division of the animal kingdom. 
APPENDIX. 
Generalities, PHiLoasNESis, &c. 
1. Agassiz’s critique of Hackel’s Gastroea-iheory (in the “Embryology 
of Ctenophorce*') is reprinted in Ann. N. H. (4) xv. pp. 87-62. 
2. Dohrn, der Ursprung der Wirbelthiere und das Princip des Func- 
tionswechsels. Genealogische Studien. Leipzig : 92 pp, (Review, 
Arch. sci. nat. liv. pp. 97-108). 
3. Elsberg, L. Regeneration, or the preservation of organic molecules ; 
a contribution to the doctrine of evolution. Pr. Am. Ass. 1874, 
pp. 87-103. 
