40 EMBRYOLOGICAL MONOGRAPHS. 
31. Radial section of a more advanced germ. The pairs numbered (2) and (3) constitute the second series of 
mesenterial septa, the single septwn, (4), arising later ; a corresponding single septum (not shown in the 
figure) arises diametrically opposite (4). 
Nore. —The numbers in parentheses indicate the order in which the brothers Hertwig claim that 
the septa must have arisen, the septum uumbered (4) being in their opinion really a pair of septa. 
Compare figures 35 and 36. 
é ~ 
32-34. Actinia equina. From Etienne Jourdan, Recherches zoologiques et histologiques sur les Zoanthaires du 
Golfe de Marseille. Ann. sci. nat., sér. 6, zool., Tom. X., Art. no. 1, Oct. 1880. PJ. XVI. figs. 117, 118, 120. 
32. Longitudinal section, showing the secondary infolding to form the esophageal tube (phx). 232. 
33. ‘Transverse section of a stage with eight partitions (2 2f.), of which the membrana propria forms the axes. 4°. 
34. Larva with small tentacles, ta.; ec’, ectoderm of the esophageal tube. 4;. (Longitudinal section. ) 
35, 36. Adamsia diaphana. From Oscar Hertwig und Richard Hertwig, Die Actinien anatomisch und his- 
tologisch mit besonderer Beriicksichtigung des Nervenmuskelsystems untersucht. Jena; Gustav Fischer, 
1879. Taf. I. figs. 3, 4. 
85. Cross section of a young Adamsia in which the fifth and the sixth pairs of ‘‘septa” are still destitute of 
muscle fibres. 
36. Cross section of an Adamsia somewhat older than the preceding. The fifth and sixth pairs of septa, although 
exhibiting muscles, have not yet joined the pharyngeal tube. 
The Roman numerals indicate the ultimate grouping of the septa into pairs in the adult animal. 
The Arabic numerals are used to indicate the supposed order of appearance of the 6 primary pairs of septa, 
the 5th and 6th appearing, however, at the same time. 
The pairs numbered 3, 3, and 4, 4 are called ‘‘direetion septa” by the Hertwigs. 
37. Thirteen figures illustrating the scissiparity of Aiptasia lacerata. From A. Andres, Intorno alla scissiparit& 
delle attinie. Miftheilungen a. d. Zoolog. Station zu Neapel, Bd. I11., Heft 1. 9 Dec. 1881. Taf. VIL. 
The letters correspond to the successive epochs of observation, as follows: 4A. 7 Noy. 9 A. M.; B. 7 Nov. 
12M.; C. 7 Nov. 12: 20 p.M.; D. 7 Nov. 12:30 P.m.; E. 7 Nov. 12: 40 ep. u.; # 7 Nov. 12: 50 p.m; 
G. 7 Nov. 1 p.m.; H. 11 Nov. 3 Pp: m.; LZ 12 Nov. 3 p. m.; J.-19.Nov. 10 A. w.; K- 25 Nov. 3p. af. 
The unaccented letters belong to figures giving the general aspect in profile. B, D, and G@ are natural size ; 
Tand K, magnified two diameters, represent only the newly-formed individual. The letters with a single- 
accent pertain to figures exhibiting the appearance of the base, and those with a double accent to figures 
of radial sections. €', E', and G! are magnified between 2 and 3 diameters; H’5 diam. ; J’, and K!, 6 
diam. ; C!, and KA’, 15 diam. 
The parent has 96 mesenteries. Of the intermesenterial chambers the 12 primary are designated by the 
odd numbers from 1 to 23, the 12 secondary by the even numbers from 2 to 24, the 24 tertiary by the 
accented numbers 1’, 2', 3’, ete. (not reproduced here), and the 48 quaternary, or spurious, mesenteries 
are not numbered. Neither of the gonidial chambers is involved in the changes. 
At stage B the disk of the foot exhibits a gibbosity which is opaque at the margin. A radial longitudi- 
nal section shows in this stage, as also in the next (compare C’’), that it is due principally to a thickening 
of the eutoderm, which soon occupies all the available space in the chambers. (The ectoderm in C” has been 
drawn relatively too thick.) The region embraced in the gibbosity is embraced between the numbers 1 
and 9. 
In the next stage (C? and C") the gibbosity is distinguished from the rest of the periphery by two angles, 
which correspond to the two chambers I! and 8/. 
In stage D the angles correspond to the chambers 2and 8. The laceration of the mesenteries embraced 
between 3 and 7 now begins. 
In the sueceeding stage (Z’) upon the base the laceration is completed in the median space, and is also 
extended to the chambers 4 and 8, nearly isolating the gibbosity, which now remains attached by only two 
delicate cords, — remnants of 3and 8’. The ragged edges contract toward the principal mass, whether of 
the parent or the off-shoot, gradually determining the contour. : 
The final separation (@‘) is effected at points corresponding to 2’ and 8!. The process thus far has occu- 
pied only one hour. 
Four days later (H’) the basal portion of the parent shows the arrangement of restored mesenteries and 
chambers, and the contour shows that the scar is healed. The off-shoot is thickened and rounded ; the mes- 
enteries at its extremes are fused together into a uniform obscure mass. The chambers which persist are 3, 
3/, 4, 4/, 5, 5', and 6, together with the intervening ones. A sagittal seetion perpendicular to the plane of 
separation shows that the off-shoot has an opening where its continuity with the parent was severed. This 
opening is restricted by the margins of the internal parts, which tend to curve inward at all points and, 
