THE 
MONTHLY MICROSCOPICAL JOURNAL. 
MAY 1, 1875. 
l.~Further Besearches into the Life History of the Monads. 
By W. H. Dallinger, F.E.M.S., and J. Drysdale, M.D., 
F.E.M.S. 
(Read he/ore the Royal Microscopical Society, April 7, 1875.) 
Plates CII., CIII., and CIV. 
This paper will complete the present series of researches — com- 
menced some four years since, and terminated at the close of last 
year — on the developmental history of monads. At the close of 
DESCRIPTION OF PLATES CII., CIII., AND CIV, 
Fig. 1. — Zonal arrangement of monads as seen in moist developing cell— a 
portion only of the field. 
„ 2. — A typical calycine. 
„ 3. — The semi-amoeboid condition preceding fission, 
„ 4. — The first stage of fission, where the base of the flagella has split into 
two, and the sarcode is opening in the direction of tlie arrows. Carrying 
a pair of flagella, a, 6, in each direction ; and the nuclear body is also 
dividing. 
„ 5. — I'ission continued. The sarcode is still moving in the direction of the 
arrows. The "nucleus" is more parted, 
„ 6. — Fission continued. The body of sarcode is now " bean shaped " ; the 
motion is still in the direction of the arrows. The "nucleus" is 
wholly divided ; and the first symptom of division of sarcode is seen 
at a. 
„ 7. — Fission continued. The flagella are opposite each other ; distinct con- 
striction is visible at a, and each part is pulling in the direction of the 
arrows. 
„ 8. — Fission continued. The aspect immediately before partition, 
„ 9. — The lialves produced by fission have only a pair of flagella instead of 
four. This figure shows how the pair are divided into two, each by 
attachment at the ends 6, c, and rapid vibration along the whole 
length, causing splitting at the ends 6, c. 
„ 10. — The flagella split by vibration, 
„ 11, 12, — The amoeboid state which precedes sexual union. 
,, 13. — The same in an extreme state, as often seen. 
14. — The blending of two in this condition. 
„ 15. — The sac resulting from the perfect fusing of all the parts of each with 
the other, 
„ 16, — This sac in its completely developed state, gently opening and pouring 
out sporules, 
„ 17, 18, 19, 20. — The spores developing in different stages until they reach the 
parent form. 
All the figures are magnified 2600 diam,, except 9, 10, 15, which are magnified 
5000 diam, and reduced. Figs. 17, 18, 19, 20, are each x 5000. 
VOL. XIII. P 
