ProtistplaDktoii. 



1 bi-aiiclios of tlu' 

 (luito eonTs|H»ii(l ti 

 rhuloiihoni). 



(hirsa 

 Ihcii- 



CIV. 



full her 



iiKk-i 



(//(// 



Fig. VII. The Cam] 



.strongly bent towards ea 

 opines unite at tlio [loint.- 



Ill ('iiiiijii/hifKiitliii. the 

 primaiv verticil of braiidics 

 is wanliiii;. lii.stoad of this, 

 .seeoiulary branches (spines) 

 are (leveloped on the 3 cdfres 

 of the main sj)incs. It seems, 

 therefore, most natural to 

 derive Campylavaiiiha from 

 the common yi'onnd form, as 

 a parallel form to Phijjia- 

 (■(iiitliii. It is, however, also 

 possible that the verticil of 

 branches is transformed into 

 the scattered, strong spines 

 on the edges, as this primary 

 verticil appears to occur on 

 the apical spine (?). 



The two basal sagittal 

 spines. 1) and V, are in Cam- 

 I (itlicr. Let us suppose that 

 and we siiould have a sagit- 



2)!/lac(iiitliii 

 these two 

 tal ring. 



It would be interesting if the ling forms (Steplwidea Hck.) as 

 a whole could be derived in a similar way; but I am as yet un- 

 able to judge if this be so, as my personal acquaintance with these 

 forms is too deficient. In the material under examination, only 

 one of these forms occurred, Dictyocircus chtthrafus, and even that 

 was very sparsely represented. It seems, however, to me that this 

 form most naturally may be derived in the manner mentioned. Such 

 a derivation seems to be natural for the division Semantida Hck. 

 I think, however, that the whole division Stephoidea Hck. requires 

 a thorough revision. 



By help of the secondary lateral spines 1, (cfr. fii;-. VT and 

 fig. VII) it seems that Dictyocircus dathratus may be quite natur- 

 ally derived from Campylucantha cladophom. (Cfr. further under 

 Dictyocircus). In this way too the long, protruding free spine, the 

 apical one A. which is not seen in IIakckkl's rin;:- forms, is ex- 

 plained. 



We also lind a clear and easy transition from Dictyocircus to 

 Ceratospyris hypertiorea, additional meshes appearing on both sides 

 •of the ring. The transition here is so evident that — as mentioned 

 under Ceratospyris — there may be some reason to suppose that 

 Dictyocircus is but a young form of Ceratospyris. 



That the network in Dictyocircus develops into the two lateral 

 ■domes of Ccratosiiyris, seems ([uite natural. Several of the most 

 important meshes are directed oblicjuely outwards from the ring 

 (cf. under Dictyocircus). The additional growth therefore at first 

 causes the network to be widened laterally. Later, byspines will 

 be formed on the sides, and these will converge towards the open 

 central space, for the direction of the byspines is generally such 

 as to cover uni)rotected places. Thus the netwoik of the sides 

 converges and the shell is finally closed. 



My opinion, therefore, is that the ring in Dictyocircus is basal, 

 not apical, as in similar foi'uis accordin:: to Haeckel's interpre- 

 tation. 



In the second scries, there is after Plictacantha the develop- 



ment lit a ventral .sagittal spine. 1 think I have seen a form which 

 would beloiiL.'- Iierc, very similar to I'lcclunnitha oikishos. but having 

 a ventral sagittal spine; but, as the study of the stuctiire of these 

 forms has taken a great deal of time, [ have been obliged, for the 

 present, to give up the thoutriit of attaining definite clearness with 

 respect to the limits for the dilVerent sjæcies. it would al.so have 

 proved impossible to di.stingiiisli with certainty between young ftmiis 

 of ditlerent .species and genera, unless the most important structural 

 conditions had first been settled. 



Krom the /'Icrtucantlui type, there is a further development 

 to J'hormacanllui liystri.r. a venti-al, sagittal spine a.s well a.s .several 

 ai'ches being (leveloped. These arches arc apical, extending from 

 the apical spine to the three ba.sal ones or to the primary basal 

 arches. I have not found time to study the course of these apical 

 arches more closely; but there regularly appears to be one from 

 the dorsal branch of the apical .spine (d,| lig. V) to the dorsal 

 branch of the dorsal main spine, one from the right branch of the 

 apical sjiine to the right lateral arch, l^^ as well as one from the 

 left l)i;nicli u\' the apical .spine (here the apical spine has the 

 piimary verticil of branches) to the left latei-al arch, ]{|. 



Besides these, there are al.so secondary apical arches outside 

 the primary ones, distally, or between them. 



It is interesting to note that Phormuranthit hystrix shows the 

 same course for the primary branches and the primary arches as 

 Flectacantha oikishos. Only in the case of Flwnmumitha. the for- 

 mation of arches has reached a further stage and the tips of the 

 branches have mostly disappeared (the branches have become parts 

 of the arches). Similarly, the outer branches of the primary ver- 

 ticil of the lateral main .spines are retrograded and on well devel- 

 oped individuals transformed into short spines. The ventral, sagittal 

 spine is bent more downwards than the lateral ones, these being 

 dii-ected more forwards and the apical one more backwards. Thus 

 is formed an interesting type, which in one respect exhibits a re- 

 markable likeness to the Cludosccnium type, while it is, on the 

 other hand, difficult to separate with certainty fiom H.\eckkl's 

 group Movocyrfida. 



The spine which H.\eckel, in Cladoscenium and the whole 

 group Monocyrtidu, calls the apical spine (apical horn) is the same 

 which I have called the dorsal, basal spine, I). Closer considera- 

 tion will prove that this opinion is Justified (cfr. under Phonn- 

 acanthu, Cladoscoiium. Peridium and LithomeUssa). Similarly to 

 the foregoing ought, therefore, Cladoscenium and Mmiocyrtida, as 

 well as the other Cyrtoidcu. to be placed in the contrary position 

 with the .,ce2)halis" (Hck.) downwards, and not a-s IIaeckei, has 

 done, with the rephalis upwards and the ..thorax" and the ..alidomcn" 

 downwards. One would get the same relationship between the 

 groups if one retained Haeckel's method of placing them for 

 Cyrtoidcu, but turned the preceding ones over .so that the three 

 spines (Haeckel's .,basal tripodium") turned upwards, and one 

 — according to the above designation the apical one — downwaids. 

 In this way, the network in Plerturunthu and Phormncuutlui slmulil 

 be considered as apical, not biisal. 



If, however, one goes in the natnial order from the simi)le 

 forms, without a network or with a very incomplete one. to such 

 ones as the Cyrtoidcu, it seems most natural to consider the three 

 spines — as above — to be basal, not apical. 



On the whole, perhaps this is the right place to say a few 

 words about the natural position of balance in the water. 



